By Ryan Dilley BBC News Online, Potters Bar

As the UK absorbs the shock of yet another horrific train crash, the painstaking work has begun to find out what went so wrong at Potters Bar. The car park at Potters Bar station is a sea of white hard hats and bright fluorescent vests.

The only ordinary people mingling with the police and railway investigators are commuters coming to pick up the cars they left here on Friday morning - when familiar Potters Bar station would hardly warrant a second glance.

Now many of these locals stop to stare disbelievingly at the scene of utter destruction.

Carriage 365526 sits wedged at a rakish angle under the roofs of platforms.

It is prevented from toppling over by steel supports which look like toothpicks in comparison to its huge bulk.

Flowers placed in silent tribute to the victims

The path of the careering carriage is easy to follow.

The side of the road bridge where the final section of the speeding train began its fatal spin is badly battered. The thick grey steel folded over like a napkin.

Where the carriage first struck the station's concrete platform, rests a twisted pile of metal and wheels, just identifiable as the car's detached chassis.

As it rose up onto the station, 365526 swept away everything in its path.

Once sturdy lampposts have been uprooted and are bent like straws.

Matchwood

The poles holding the station sign fared no better.

They are listing badly and their large placard bearing the name "Potters Bar" has been ripped from it mountings and tossed far across the track.

Much of the waiting room has been turned to matchwood.

Its benches lie upturned amongst the splinters and broken windows.

Amid the lumps of torn-up Tarmac and shards of metal, remnants of Friday's rescue effort remain.

A supermarket wheelchair stands at the scene

Besides several forlorn pieces of luggage and seats ripped from the stricken carriage, is a wheelchair brought by first aiders from the nearby supermarket.

These items will be carefully removed as the process of gathering evidence continues, says Chief Superintendent David Hatcher of the British Transport Police.

Investigators will be sifting through all the debris which marks the passage of the train's final moments, hoping to separate items scattered as a result of the crash from those which might have been part of its cause.

'Defusing emotions'

With overhead electricity lines downed, and the carriage balanced so precariously, Mr Hatcher says the job his officers face is a potentially dangerous one.

But with so many dead and badly injured in this disaster, the process of piecing together what happened at this quiet suburban stop also takes an emotional toll on those working around the scarred carriage.

As chaplains mingle with the teams readying themselves to venture on the track, Mr Hatcher says that a concerted effort is made to "defuse the emotions" evoked by such a difficult duty.

"Some of these officers were almost certainly at [the] Hatfield crash too," he adds grimly.