Protecting London – Police use of aerial imagery

Sgt Richard Brandon

In this talk I am going to try to take you through a little bit of what we do in the Air Support Unit in London. I would like you to go away with an idea of what we do operationally over London - what the noisy Police helicopters are doing over London - and how we do it - we will look at the aircraft and the technology that we use and the advances that we have had over recent years. Then we will end by looking at the imagery, the live analysis of that imagery by trained air observers, the offline analysis of imagery and the future use. But first of all I would like to start with a little bit of the history.

Police aviation is nothing new! In 1914 Punch magazine produced a cartoon which talked about the fact that the Police might use airborne imagery. Indeed, by the 1920s the Police were using airships because they had started to realise that the best way to get a good view of an event was from an airborne perspective; a bird's eye view. Over the next sixty or so years, the police aerial presence adapted into the use of helicopters. This began in the 1960s when the Army were lending the Police helicopters. Over the course of the next few years, they realised airships were good but that they were not as dynamic as a helicopter and they are not able to get around as much. So they hired in helicopters, and by 1980, the Met Police realised that police aviation was something where it needed to be; that the capital city needed this added layer of security. Therefore, in 1980, the Air Support Unit was formed at Lippitts Hill and the Met Police bought three of their new Bell 222 helicopters.

The Bell 222 was a luxury helicopter. It was designed for VIP transportation, with things like leather seats etc. They are still in use around the world today. It flew over London doing public order tasking; looking after major sporting events, major demonstrations and major ceremonial events such as Trooping the Colour, etc. It continued to fly until the mid-1990s, when legislation changed. The Police found that the Bell 222 could not satisfy the needs of the Civil Aviation Authority, the legislation that said you had to have certain levels of performance, capability and instrumentation.

So the Met bought three twin squirrels, as they are affectionately known, and these are the helicopters that flew from 1993 right up to 2007 over London. You will have seen them, marked up the same as a Police car, and they were a very capable Police helicopter, but like everything, things change. As society evolves, the role of the Police evolves, and what we found was that we were getting operational demands that we could not fulfil with this helicopter, so it had outlived its shelf life.

In 2006, we bought three EC145 helicopters, which is bigger, more powerful and modern, and it allows us to do a great deal that we wanted to do before but could not due to the limitations of the Bell 222 helicopter. The EC 145 helicopters entered service in June 2007, after nearly a year and a half spent designing it, working very closely with the integrators in making sure it had the right technology and that it was all fit for our purpose. To date, we have flown 4,500 hours across our fleet of three already. They are the most advanced Police helicopters in the world. There are a few in the pipeline that are going to be taking our crown soon I think with technology, but at the moment, they are about as good as it gets.

But what do we actually do over London? We do travel nationwide to a certain extent, but primarily we are within London. We fly about 3,300 hours a year, which equates to roughly nine out of every 24, over London, and we deal with in excess of 10,000 different tasks. I am going to explore some of those tasks this afternoon, just to give you a flavour really of what we do and why we do it.

Searching is by far the most common thing that we do. We primarily use the helicopter as a search tool. It flies with a crew of three: there is a pilot and two Police Officers. The front seat Police Officer assists the pilot and controls the camera, and the rear seat Police Officer is the tactical commander of the aircraft. They do all the communications and they work out exactly what to do, when to do it, and where to do it. To give some sort of idea what the searches might be for, a list might include such things as searching for suspects at-large following burglaries and robberies, searching for missing and vulnerable people, searching for security purposes prior to or during an event, and many other things besides.

We also manage pursuits. We are the primary asset within the Met Police pursuit policy for deployment over a pursuit. You have probably seen the television programmes so you can imagine how dangerous pursuits are: there are risks to the public, to the Police Officers and to the people in the car being pursued. Pack that into London's dense and busy streets and it suddenly becomes extremely dangerous. The Air Support Unit provides the ability to look at this pursuit from a withdrawn aerial perspective, without the need for police cars. Therefore, we can withdraw the Police cars and take away some of the danger, and we can monitor the pursuit until the people decamp from the vehicle, and then we get the opportunity to arrest them or to deal with them. Because of this we are a very key asset. Pursuits in London tend not to be that long, but when they do go on for twenty or thirty minutes and the helicopter is a wonderful asset at maintaining the maximum possible safety during that time.

We offer tactical support to the 30,000 London Police Officers and the PCSOs. The Air Support Unit is of great use to almost all kinds of events where you have got Police taking control of an area. Whether it is a domestic siege, some form of fire or a road traffic accident, wherever there is a need to coordinate resources the helicopter effectively is an airborne command and control platform. We will see some of the technology that we have at our disposal to enable us to do that.

We are also highly important in armed incidents. London is an increasingly armed city. I personally hope that we do not ever see the day that the Police are armed, but we do have armed Police on the streets of London and we have criminals using weapons. We work very closely with armed officers in making their jobs safer. We have had cases, throughout the UK, where Police have not been able to go into a rear garden, for example, of a house because there is a fear that the armed gunman, who has shot someone, might be there. The person in there might need our help, they may die if we do not give them the first aid that they need, and the Air Support Unit allows us to get an airborne perspective so as to give good information to officers on the ground so that they can do their risk assessments and they can get in there and do the job that they want to do.

Aerial imagery is increasingly used by the Police, for planning, for prosecution, and for all kinds of contingency and emergency situations. We are the primary source of airborne imagery, both evidential and non-evidential, and in fact, we are also increasingly moving towards airborne surveillance. So we work under the Regulation of Investigatory Powers Act, otherwise known as RIPA, and where we are authorised to do so, we conduct directed surveillance. You might think that is strange, but a marked Police helicopter over London, nine hours a day, apart from the noise, people almost do not notice that we are there, and even then, we have got tactics that allow us to detach ourselves from where we are currently looking.

In all, there are probably forty options of what we do in the Air Support Unit. I won't bore you with all of them, but I have at least given the major functions and given you a taste for what we do.

At the very top of the list of the Met Police's primary aims is to work together with others for a safer London, and our primary goal is improved Police and public safety. A part of this is preventing and detecting crime. We do this by assisting the Met Police by focusing our patrols and efforts to help them to deter criminals and detect and prevent crimes. We are securing best evidence: we are providing that piece of the jigsaw that they need to gain a conviction in court; helping them to paint the picture that the jury need to establish what happened. And we are gathering intelligence. So at the top level, this is what drives us as at the Air Support Unit to do what we do.

What value do we add? People often say, "Well, what do you actually do? What value do you add to policing in London?" Well, we reduce risk, and I think everything that we do, at the very heart of it, are the questions: does this reduce risk, does it make London safer, does it make it safer for the Police officers?

There have been high profile cases. The Commissioner was prosecuted under the Health and Safety legislation for an officer that fell through a roof and died. It is no longer acceptable for Police officers to go onto roofs, railway lines or into water, not because they do not want to do it, because I can assure you, as a sergeant supervising PCs, they will go where they need to go and they want to do the job, but it is not safe to do so. Therefore the presence of a Police helicopter is of utmost importance to clear these areas very quickly and very efficiently and so the Police commanders on the ground do not have to make those difficult decisions. What do we do if we think the suspect is on the roof and we haven't got a helicopter? Can we search it? Do we let them go? Do we risk putting officers up there? So there is an awful lot of benefit that we add. This can be done very quickly as it only takes two or three minutes to get a helicopter on the scene, and we can clear a roof and say, "No, they are not there," or "Yes, they are there," and we will contain it whilst the Fire Brigade or other properly trained and equipped Police Officers get there.

We are also releasing valuable resources to other tasks, for instance, the fact that you have a helicopter that can search a large area very quickly and very efficiently means you are not tying up your valuable Police resources on the ground doing a job which might take them several hours. We are delivering increasing scarce specialists and specialist kit from A to Bquickly. Invariably, when an incident happens, like the bombing on the seventh of July in London, what happens is gridlock as the road and public transport networks shuts down. Not only can you not go about your business, but we cannot go about ours either. We cannot get from A to B, and what we are finding is that there is an increasing number of specialist departments in the Met knocking on my door saying, "I've got this kit, I've got these people - would you be able to pick us up in this school playing field and drop us off on the other side of London quickly, if we had such an incident?" We are now carrying out and expanding those roles.

As I mentioned earlier, searching amounts to the biggest proportion of what we do: about 60% of our work is search-related. That means that most of work, which is search-related, is spontaneous and demand-driven, so we cannot predict exactly when it is going to come in. We know about some of the security searches, but the vast majority is happening now and we need to go and deal with it immediately.

The Home Office did research in the 1990s that looked at a comparison between airborne assets and foot assets. It searched a certain area for a certain number of controlled items, and they found that the airborne study was by far the most efficient. That was in the early 1990s, when technology was nowhere near as good as it is today. We are actually waiting for them to re-commission the same study, so we can see just how efficient we are now. But the Police on the ground, with police sniffer dogs, have a role to play, but what we want to do is clear maybe 90%, leaving them to concentrate on the 10% where they are best equipped and best trained for it. That saves time and it saves money.

Hackney Marsh is a good example of this. We were recently asked to search the Hackney Marshes area, which is quite a large area. It took us twenty minutes to clear Hackney Marshes by air and say that the person, a vulnerable missing person, was not there. We were talking to a Police Search Advisor, who had done an operational plan for seven Police Officers taking eighteen hours to search the same area, so here the figures speak for themselves. It is clear from this that we are cost-effective. We might be an expensive asset, but in terms of policing, we are cost-effective. But, let's now move on and look quickly at how we do it.

At the very heart of our aircraft is a stabilised camera system. This is effectively a television camera that is housed into a gyro-stabilised turret. No matter what the helicopter does, you get a lovely, stable picture on screen. It is an incredibly high magnification daylight TV camera that allows us to look at a whole housing estate, or down at an individual house. We also have on there a telescope, a spotter-scope, which effectively allows us to read a number plate, or to look at the front door, or to look at someone's face. We have just recently upgraded to give us a night-time capability on that, a low-light capability, that will see in almost total darkness. But the main camera that we use for searching is the thermal infra-red camera, and I am going to talk a little bit about that, because I think that is probably the most unusual and most interesting area of Police technology.

So, what do we do with thermal image; why do we use it? - Fitted to each of our helicopters is a state of the art piece of equipment, several hundred thousand pounds worth, as used by the military in Iraq and Afghanistan. With this, the aircraft is kitted out like a mobile command and control platform. There are five mission screens in there, and they are all interfaced together through a unit called the video management system. What that allows me to do, as a member of the crew, is to watch any of the video pictures, on any of the screens. I can record anything, I can view it, and I can link it together with others, and I can down-link it, broadcasting it live into a control room or to an officer on the street, and all of that is done through an array of television screens within the helicopter.

The rear tactical commander has two 15-inch displays, each of which is capable of displaying four video images. It is the job of these air observers to filter through this massive amount of information and use this technology to good effect.

The front observer sits in the front left of the helicopter. They have a ten-inch display. Again, it is touch-screen, so it allows them to do anything very quickly and easily, and we worked very hard, when designing the aircraft, to make sure that what we had was a machine that was user-friendly, that the Police Officers could actually use. This is half a matter of simplicity of use, but also half a matter of ease and quickness of use, because if it can't be done immediately, then it simply won't do for police use. The technology we have got is very, very user-friendly. The interface between the human and the machine is very sophisticated but intuitive.

The front left seat, as well, operates the camera, so any of the camera pictures that you ever see, it is this person in the front left that is doing that camera work, and they are navigating to the task as well, making sure we get there quickly and efficiently.

The pilot, of course, is essential because the others cannot do the job without them. Most of our pilots - in fact, all of the pilots at the moment - are ex-military pilots, although that is not a prerequisite for Police flying. They are all extremely experienced aviators, with several thousand hours flying helicopters, and they need to be at this level because we are flying lower, closer and in poorer weather than you would expect most normal helicopters to fly. The reason we do that is because, much like the Road Traffic Police have easements as to the Road Traffic Act, allowing them to go through red lights and exceed the speed limit etc., we have easements over the Air Navigation Order. This means that we can fly lower, closer and in poorer weather.

So the pilot is a key part, and what we have built into this helicopter is a screen for the pilot. It is again touch-screen, it has mapping technology, and it has the ability for them to see what we are looking at. That is of paramount importance because the pilot is key to getting the aircraft in the right position. If a suspect runs round the side of a building, and we are not on the right side of that building, we will not see them. So the pilot has to anticipate what might happen and their job is to try and give the Police Officers the best possible view of what is going on.

At the very heart of what we have got in the aircraft is quad-screen technology, which gives us four screens of essential information. The top left screen is a wide-angle daylight picture to give a nice situational overview of, for instance, what vehicle I am looking at. This is particularly useful if I have to describe to ground officers where the vehicle is. On the top right, we have got the spotter-scope which gives the details that can't be seen in the wide-angle shot. For instance, it might give me the number plate and the detail that I need. Bottom left is the infra-red picture, which is particularly useful at night. Then we have a moving map on the bottom right, which is fully interfaced with the camera. This moving map shows me, for example, that this vehicle that we are watching is travelling down the A13 at 79 mph and is heading southeast.

I have got all of this information presented to me on-screen, as an air observer in the aircraft, enabling me to make tactical decisions to give good advice to officers on the ground. So it needs to be very accurate, which it is because the camera system is linked to a mapping system. This means that the camera knows where it is pointing and it knows what point on the Earth it is currently looking at. It does that through a piece of technology called an inertial measurement unit, which basically allows the camera system to communicate with the mapping computer to give a very accurate camera pointing. So, on the one hand, I get a picture on a map that shows me exactly where the camera is looking, and on the other hand, I can pick a location on the map, send it to the camera, and have the camera point at that location, so we get a thing called camera slewing. The two of these elements work really well together and they give a good amount of situational awareness.

We have four video recorders on the aircraft. They are solid state, so we have moved on from tape. A few years ago, we were on VHS, then we moved to digital video, and now, we are into solid state, and we are recording MPEG2, which is near to DVD quality, and we are recording onto a little flashcard. That means that, with the four video recorders, we can replay the video in-flight. So if we the suspect, for example, runs away from a vehicle and we lose sight of them, and then they are found by a police dog or by a dog handler, we can put the suspect that has been found together with the picture of the suspect leaving the car and see if it is the same person, and we can do that live, in the air, and then we can record that. So it is very clever technology, and because there are four recorders, we can record three different evidential sources, and one to replay in flight.

At the very heart of what we do in the air, this command and control platform, has the ability to broadcast those pictures down to Earth. The Media have been doing this for years. Whenever you see aerial pictures of the Marathon or any event, they are sending those pictures via microwave from a helicopter down to the ground, and we are using exactly the same technology. It is encrypted so it is secure, and whatever I, as an observer, choose to send to the ground is going from the helicopter down into a network of portable and fixed receivers. Those portable and fixed receivers are based at various sites around London, giving us coverage over the whole of the metropolitan area, and probably several kilometres beyond. What that allows us to do is to give that tactical information right into the hands of the Police Officers on the ground who are making command decisions at silver or gold level or even bronze level. So they are determining tactics and deciding what to do by means of the images we are capturing from the helicopters.

Also, we are expanding the use of portable receivers. Many of our specialist teams, such as Firearms, Dogs and Special Escort, have access to a little handheld unit that, again, gives them live video pictures in their cars, in the streets, near an armed incident or whatever, so they can see what we can see. So they can see the backs of premises, the rear gardens, what the doors look like and whether the suspects are there, etc. This is a real growth area, and we are going to see, over the next four or five years, more and more use of digital downlink, pushing those pictures out where they are most needed.

What we have also got is the ability to broadcast pictures from the ground up to the helicopter. What that means is that we have got a fixed transmitter on the roof of Scotland Yard, that can send pictures up to the helicopter from any of the CCTV cameras in London, but what we have also got is a range of portable transmitters that would allow us to broadcast surveillance pictures, or other locally based pictures, up the aircraft and back into our Special Operations Room. So again, we are really expanding this area of expertise. In this we are almost entering the television world, where we are sending pictures and sound all over the place, giving people information they need to do their job.

You will probably have heard of automatic number plate reading, which is a technology that is now fairly widely used. We have got it fitted to the aircraft. We are not quite using it operationally yet, but we are training with it at the moment. It is actually remarkably efficiently because it will clear a Tesco's car park in a matter of minutes looking for a particular vehicle, which is much faster a human being could do.

One of the biggest developments we have got on this aircraft is the tactical command. We have actually got a dedicated position on the aircraft to allow us to carry a senior Police Officer or a Fire Officer or a Tactical Advisor, and we are doing this on a fairly regular basis. In fact, we have got demand from the Ambulance, Fire Brigade, Transport for London, and others, to work together with these other agencies to do the job; to do policing and to make the capital safer. If we are there providing pictures, like we were at the Royal Marsden fire, why can't we give those pictures to the firefighters that are trying to fight that fire? We realised that we can and they have the technology to receive the pictures.

They are also talking to us about how we are to get key people, such as medical teams or specialist fire-fighters, across London to where they are needed if we get a major incident within London, like the seventh of July. It may well be that the Police helicopter is the way to do that.

We can get a better understand of the types of things the Air Support Unit does if we look at how the technology helps us to carry out certain tasks we would not otherwise be able to do. A prime example is the infra-red camera. With this, we can quickly identify heat sources. The heat source may be an animal and with the old technology you really could not tell whether it was a person or an animal, and you used to have to light the thing up with a search light to see. But this infra-red camera now allows us to determine whether it is human or animal perfectly.

This camera means that we can see a suspect in the middle of the night, in complete darkness. But we use the infra-red even in daylight. We work on the basis that all objects either reflect infra-red radiation or absorb and then transmit it - everything does, and they all do so to a different degree of efficiency and a different level. We are primarily looking for an active source of infra-red. So we are looking for our suspect who is hot, because they are running away from the police, and because of that, a lot of searching is looking for active IR signatures. However, there is a whole area of research to be done into passive IR signatures - this is what impact does the sun having during the day on an object. I will give you some examples of that later on, as to where we think that might be useful. But the vast majority of Police imagery is active.

The primary role of an air observer in searching is that they have to understand what they are looking at on screen. So experience tells an air observer "Is that dot of heat in the right place? What is it? Is it worth having another look at?" It is extremely important that we train our observers and they get that experience to enable them to do what is a very tricky job. An example of this might be a person jumping into the Thames where we might only see the top of their head. It might be a dot in the water, and the observers need to be methodical and have the Police Officer's instinct that gets them in there and gets them looking at those heat sources.

Another good example that I have seen was where a family was robbed at knifepoint and then the suspect ran off into some allotments. The helicopter crew were searching for a good half an hour, just about to give up, and one of the observers, probably one of my most talented observers, had said, "Look, that shed door, why would it be getting hot?" When they focussed in on it, they saw that it was because the suspect had his knee up against the door of the shed which was making it get warm. They then called in the Firearms team and they found the suspect coming out of the shed. So again, it is about being methodical and knowing the signs. You could easily have flown away and said there was nothing there, but there was a massive amount of satisfaction that we get from getting a positive result.

Another good case study is one where the suspect chased and lost by the Police in an estate of several streets, each with rear gardens. The ground police then had very little to go on to try and find the suspect, but from the air, the we could see that in one of the gardens there were two wheelie bins with one hotter than the other. It may have been that that one of the wheelie bins was full of compost - because as compost decomposes, it produces heat - but could also have been that our suspect was in the wheelie bin. So we asked officers to go and have a look, and sure enough, in the wheelie bin is our suspect. In fact, what is funny about this case is that the suspect would not get out of the wheelie bin, so they wheeled the bin along the street, with him in it, to the Police van, and then tipped him into the back of the van! But this is a classic example of how we are using this technology to help us. Otherwise, how would we have ever found them? How would we have seen that person?

We are also using the technology onboard increasingly to collect evidence. What we are finding over London is that we are increasingly being targeted by people lasering the helicopter. It manifests itself as a bright green glow that fills the whole cockpit, and it is quite dangerous. They also laser the Air Ambulance, and they laser the airliners coming in and out of Heathrow and City, which is perhaps even more dangerous. What we have had recently is a number of prosecutions. One person went to prison for six months for this, because of the evidence that our technology can provide. The first part is the infra-red picture, which is great but does not show light because it is only showing heat. So although it will give you, for instance, a nice picture of a person in a doorway, you cannot see what they are doing because it is only looking at heat, and laser is probably relatively cold. But this is important when it is paired with the daylight camera, because that will flare out the minute that the laser hits it. This will then show us that the suspect fired a laser. The mapping system will then tell us exactly where the suspect was, right down to individual house numbers. So when we go knocking on the door, they look rather surprised and ask, "How did you know?" and it is because of the technology on the aircraft.

We are constantly called to deal with incidents, whether it is fatal road traffic accidents or something else, and we are combining the use of electro-optic, which is the sort of daylight television cameras, with infra-red. This enables us to combine the benefits of each to get the best quality of image and detail. Therefore, if the daylight camera is grainy, it can be combined with the infra-red image to define it to the best image possible.

All of these examples so far are of Live use. This is a matter of trained people looking at the imagery and making a live operational judgements based upon it. What we also are finding is that we are increasingly required to look at the imagery offline. This is at a much slower pace, but we are looking at it mainly for use as evidence.

This comes in the form of many phenomena, one of which is called thermal residual. This is where the presence of a suspect leaves a slightly warmer patch even after they have gone. Because of this, even when the suspect has gone, where they were is still going to be warm for a period of time. This is proof that they were there, which often proves to be essential. After the commission of a crime, if we get there within the first 30 minutes or so, there might be something present on infra-red that we would not have normally seen; some evidence that we can analyse later, frame by frame, and have a look at. There are many well-known cases where, if only we had this technology, we might have been able to say was the vehicle there, was the suspect standing there etc. So again, there is a lot of essential policing use in this Air Support technology.

Another phenomena is thermal scarring. An example of this is found in a vehicle braking when you cannot see any sort of skid mark with the naked eye, but you can on infra-red, because it has warmed up the tarmac through friction. This is very important at scenes on accidents, especially a fatal accidents, where we might help them to piece together the bits of the jigsaw to find out what happened.

Another phenomenon is thermal highlight. A good example of this is when an object is parked in a particular location over a prolonged period of time. If this is over many months and years, lots of things happen or not according to the object's being there. Firstly, the ground beneath the object does not weather at the same rate that the ground around it does. Secondly, if it is a hot day, the ground underneath does not warm up as much as the ground around it, or conversely, at night, the ground beneath stays warmer than the ground around it. So there are lots of ways that we can use this.

Thermal shadows are an amazing testament to how sensitive the infra-red camera is. On a sunny day, we can detect where someone has just been by the difference in heat on the ground where they have walked. This difference in temperature in someone's footsteps is caused by the fact that the sun, at that moment when they were stood or walking over that spot, was not shining on that bit of ground. The heat difference disappeared in a second, but at times this is enough. And if this were not enough to show you how sensitive the camera equipment is, it even picks up "shadows" are where you have got a reflection of the heat.

By a phenomenon known as hydroponics, the infra-red camera is capable of identifying the locations where people are potentially cultivating cannabis. We are able to see that either their loft insulation is really not that good or something is going on in there that is making it disproportionately hot compared to everywhere else. Of course, in itself, that does not mean that they are growing cannabis in there. What it means is that it is maybe worth the Police having a look, looking at their intelligence database and following it through. There is no doubt that this level of criminality is linked into organised crime. So we are not talking here about people growing a cannabis plant in their back bedroom - you are talking about organised crime.

We are also grabbing stills from the video and we are using them to brief teams. This has the great benefit of being able to actually show the officers the details of locations and suspects so that the chance of a mistake is greatly lessened. So we take the video covertly, grab the stills, and give people a thorough briefing - this is where the door is, that is where we are going, this is where you are to keep the containment in, this is where the vulnerabilities are etc. So again, it gives you an opportunity to paint a thorough picture.

One of the things that we have been working a lot with our detectives on is supplying the jury with aerial photographs of crime scenes, so that they are enabled to make informed decisions about the investigation at hand. This is particularly of use when the police have to use complicated surveillance logs as evidence, where it would be very hard to understand were it not for the photography which we can provide. So, we are increasingly rolling out this kind of evidential support.

My final topic I want to touch on is contingency planning. There is no doubt about it that when big London-wide or even nationwide events happen, like the seventh of July bombings, the Police and their emergency plans have to kick in. What we have been saying for a long time is that you cannot have a thorough emergency plan if you do not have up-to-date aerial imagery. Google Earth is brilliant; it is a fantastic tool. You can go and have a look at any part of the world, but how old is that imagery? I have got a picture of my house on there, and I think it is probably at least two years old. Therefore, for the operational and contingency planners to create the best strategies possible, they need up-to-date and detailed images. In this way, the Air Support Unit is essential to efficient and correct responses to incidents like the bombings of the seventh of July.

So, to conclude, I hope my talk will have given you a better understanding of the types of work that the Police Air Support Unit is doing here in London and beyond. I also hope that you will have gathered the importance of this work and the essential part it plays in helping our colleagues on the ground do the best job they can at making London a safer place for us all.

©Sgt Richard Brandon, Gresham College,13 October 2008