It is a vista of mangled, metallic devastation so brutal that you are compelled to take a long, deep breath as your eyes widen to take it all in. Here there is a helicopter shattered like a broken toy, with mud still jammed into the Perspex cowling where it hit the ground. Over there is a veteran Hunter jet fighter, its tail burned away in an air-display accident, its cockpit smashed to pieces.

In the corner, a pile of ashes and twisted spars which, someone says, was once the Kent Air Ambulance. There are perhaps two dozen such carcasses, the dreadful harvest gathered in recent months from all over the British countryside. In each one of them at least one person, sometimes more, has died.

And towering above the lot is the most notorious wreck of them all, the painstaking reconstruction of a forward section of the Boeing 747 which became known to the world as Pan Am flight 103. A jigsaw gathered from a wreckage trail along an 88-mile corridor covering 845 square miles; the spectre of  Lockerbie, still waiting as evidence.

Ten years ago, on the night of December 21 1988, Pan Am flight 103 was torn apart by a terrorist bomb, resulting in the horrifying deaths of 270 passengers. Now, after all those years, and seemingly endless diplomatic and legal manoeuvring, the trial of two Libyan suspects, which has been delayed and obstructed by the Libyan government, is widely expected to take place this month.

Last Sunday, Colonel Gaddafi made a speech that appeared to indicate he was stalling further. However, the plan still stands that the suspects - Abdel Baset Ali al-Megrahi and al-Amin Khalifa Fhimah - will be handed over to the United Nations to be tried in the Netherlands, under Scottish law.

The echoes of these events are heard within this hangar, this place of ghosts, set alongside the Farnborough airfield in Hampshire. It is the domain of a tiny team of just 30 air accident investigators whose reputation as crash detectives is second to none in the world and whose work among the debris is crucial to future air safety.

The team, supplemented by 14 other staff, handles about 100 field investigations at home each year and is also on permanent standby - at 30 minutes' notice - to travel to anywhere in the world if there is British involvement in a serious crash, or if, as often happens, British expertise is requested by a foreign government, under international agreements.

"They are all hand-picked and they are hugely experienced," says their boss, Ken Smart, 52, who became Britain's youngest Chief Investigator of Air Accidents when he was appointed to the job, eight years ago. "Their preoccupation is with safety. The opportunity to make aviation safer is what puts the fire in their bellies."

THE investigators fall into two categories: operations inspectors, who are all former senior command pilots of large passenger aircraft, many with test-pilot backgrounds in the Royal Air Force; and engineer inspectors, highly skilled engineers who have worked throughout their careers in the aerospace industry but who, in addition, are all qualified pilots.

The ops inspectors keep up their licences by flying as captains for two or three days each month with scheduled major British carriers, while the engineers are all encouraged to fly to private-pilot standard at least, and are given flying hours so they can retain their licences.

The mix of disciplines has been perfected over the past 83 years, since the original unit was established by the Royal Flying Corps, during the First World War, and has brought the United Kingdom to the forefront in air-accident investigation. It is work that earns members of the team probably half as much as they would expect for flying or for specialist engineering in the private sector.

"But they are willing to jump that gap because they want to put something back into aviation," says Smart. "They are dedicated to improving safety standards and making a difference. Seeing their recommendations accepted and adopted worldwide is a very considerable reward." The job is not, of course for the squeamish. Within minutes of the receipt of news at Farnborough of an air disaster, a team is scrambled, sometimes by helicopter, to Heathrow to join a flight to the crash scene.

"Speed is of the essence because it is vital to know as soon as possible, what has triggered the accident," says Smart. To this end a team of three operational inspectors, three engineers and a specialist flight recorder expert is always on call at night and at weekends. Within hours, sometimes less, of being at home with their families, they frequently find themselves among the maimed and the dead at the crash scene.

It is, says Smart, "part of the territory", but no easier for that. "Coming across bodies and human remains is not the most immediately difficult thing because you do get a lot of experience of it," he says.

"The really hard time comes with meeting the families. It is then that you rationalise what you have seen, it is then that you realise that it could be your wife, your child. And when you have a light aircraft crash, when perhaps only one or two have been killed, you really get to know the families individually. You really identify with them.

"But we are all trained to deal with the nasty aspects of the job, and we have been advised how to counsel ourselves and handle it by a colonel from the Army College of Psychiatry, who advises the SAS on such things. "When we are on a big team field investigation, such as Lockerbie, we take over a hotel for our exclusive use, and we meet in the bar in the evenings and just talk it all through. "We operate a buddy-buddy system to make sure that everyone gets a chance to talk out what they have seen and we make sure that no one is sitting on their own moping over a pint of beer."

Smart emphasises to his staff the need to keep the families of crash victims and the survivors of crashes fully informed of the progress of the investigation. "We invite them here and we show them the wreckage and brief them on what we are doing. We are clear and honest with them, and we give it to them warts and all because we respect their right to know what happened and, in any case, it is part of the grieving process."

One of the most frequently asked questions is, inevitably, whether those loved ones who died knew of their fate and, if so, for how long? "They don't want to see it all through rose-tinted spectacles and there is no point in giving them a story which isn't true," he says.

IN FACT, in most cases of catastrophic failure of an aircraft at high altitude, such as the devastation caused to Pan Am 103 by the Lockerbie bomb, the passengers would have been conscious just a few seconds after the realisation of disaster dawned.

But, in other cases, such as the disaster over Zagreb in the late Seventies, when a British Airways Trident and a Yugoslav DC9 collided, the victims could have been alive and conscious of their terrible fate for up to 30 seconds, as the aircraft spun to earth. The techniques used by Smart's team have, naturally, progressed enormously since the first tentative investigations by his predecessors back in 1915.

But, curiously, in the case of sudden, high-altitude failures, which are so often the most difficult to unravel, the basic tenets remain the same. "We follow the wreckage trail and try to establish which bit came off first," says Smart. "In the old days it was calculated almost on the back of a cigarette packet but today we can use computer modelling linked to meteorological aftercasts and the reports of witnesses to help us get it more accurately."

These days, computer technology means that the AAIB can run a debris sequence backwards, reassembling the failed part of an aircraft by "flying" wreckage back to it from the place it was found on the ground. Using digital maps, it can track flights over "real" terrain, and final pre-crash sequences retrieved from flight recorders can be fed into a computer to recreate the last actions of the pilots.

And the AAIB has a database of cockpit noises, provided by manufacturers, which its experts can compare electronically with noises from the cockpit voice recorders. "You can get all sorts of clues, not from just what the crew are saying but from the noises going on in the background," says Smart.

With flight recorders becoming more sophisticated and with modern aircraft transmitting state-of-flight data to their companies at regular intervals during flights, investigators have never had so many potential sources of pre-crash information. "When you think of all the microchips now used in aircraft and realise that each may have a story to tell, you can see that the amount of data we get is the challenge now," says Smart.

But not all crash investigation is down to technology. Much of the real detective work is done among the mangled wreckage by the engineers who know the purpose of every nut and bolt they find. One of the AAIB's most rewarding results came in the early Nineties, when a Tornado crashed, killing its pilot. An investigator discovered quickly that the probable cause was a failure of an aileron linkage and a message was urgently transmitted to all RAF Tornado squadrons.

A fleet inspection revealed that at least four other pounds 38 million aircraft had the same problem and could have crashed within a few flying hours. "We certainly earned our corn that day," says Smart. A bete noire among the accident investigators is the much-used phrase: pilot error. "It is not part of our vocabulary here," says Smart.

"Because, if an accident is caused by the actions of the pilot, it is our job to find out why he took that action and, perhaps, investigate his training, the culture of his airline . . . every conceivable cause of the action. It is a fact that deliberate, unprofessional actions are very, very rare."

So how dangerous is flying? "Consider this. There are between one and two catastrophic accidents per million departures and you could fly every day for 4,000 years and not be involved in an accident. And even if you were, you would have a 50 per cent chance of surviving, " says Smart. "I'd say it was pretty safe."

Peter Birkett, Weekend feature: The crash team Ten years on, the wreckage of Pan Am 103 is still at Air Accidents Investigation Branch HQ. Peter Birkett reports on the people who piece together the evidence after a., The Daily Telegraph, 12-05-1998, pp 12.