By Tom Symonds BBC transport correspondent

Nobody has been held responsible for the crash

The East Coast Main Line cuts through the centre of town. But after decades of bringing people home from work, a year ago the railway brought tragedy.

The 12.45 from London to King's Lynn was 11 minutes into its journey. It was not even supposed to stop at Potters Bar.

Thundering through the points to the south of the station it derailed. One carriage flicked off the track, and rolled up onto the platform, killing six passengers.

The seventh victim was a woman walking along a road nearby, killed by falling debris.

The points had broken apart. The bolts which were supposed to secure them were found lying discarded on the ground alongside.

DNA evidence

A year on, no-one really knows why the bolts were removed.

Memories of Potters Bar crash remain

A police investigation has taken 1,300 witness statements. DNA evidence has been gathered from the points, and CCTV footage enhanced and scrutinised for clues.

Detectives wading through maintenance records described it more as a massive fraud inquiry than an murder hunt.

They said a third of the British Transport Police was now tied up in crash investigations.

The police will finish their work this summer and it will be for the Crown Prosecution Service to decide whether charges for corporate manslaughter can be brought against Jarvis, the company responsible for the maintenance of the points, or Network Rail, which owns and operates the line.

Public inquiry

Jarvis has controversially suggested sabotage may have been to blame.

The solicitor for the bereaved and injured, Louise Christian, believes the police will conclude there is not enough evidence for a prosecution.

The government has so far refused a public inquiry and the lack of an official verdict on how this happened has added frustration to the fraught emotions of those who survived, or are mourning the dead.

No official verdict means it is much more difficult for them to obtain compensation. No-one has accepted legal liability for the crash.

Compensation

Network Rail is paying the medical and legal bills of the victims.

It is also discussing compensation settlements.

But the solicitors say with no admission of liability, they will not be able to go to court to ask for higher levels of compensation - unless they prove who actually was to blame.

Their best hope is that they will be granted legal aid in a forthcoming court hearing, so they can gather their own evidence from the crash.

Potters Bar is just the latest in a series of British railway disasters, many of which still have outstanding criminal investigations.

There is hope the railways are getting safer though. A new device is being fitted to stop many crashes caused by trains failing to stop at red signals.

But no-one can be certain there will not be another Potters Bar, another police investigation, and another group of passengers and families, who lives are changed by tragedy on the railways.