A vision of hell on 7/7 Tube train

This is the first image of the devastation wrought on a Piccadilly line Tube train in the 7 July terror attacks.

Forensic science officers comb the charred, mangled ruin of the carriage where bomber Jermaine Lindsay murdered 26 people.

Working in 60C heat in filthy, claustrophobic conditions, the investigators search for clues in the debris under Russell Square station.

The picture was taken by a police photographer a few days after the atrocity four years ago - Lindsay was not identified as the killer until a week after the attack.

The remnants of the carriage show how powerful the force of the explosion was in the 11-foot tunnel.

The shattered window frames and the twisted metal only suggest how hellish the conditions would have been for the passengers on the rush-hour carriage.

Indeed it is remarkable that there were any survivors, when looking at the melted and warped floor of the carriage and the missing metal poles blown away by the bomb.

In this image, an officer crawls along the floor conducting a fingertip search under bright lights while another looks for microscopic evidence on a seat.

There was no ventilation as the tunnels were blocked to prevent clues being blown away by gusts.

The forensic teams were initially able to work only for 20 minutes at a time on the train before emerging for air.

As one officer said after the blast at Russell Square: "I don't know what heaven looks like but I have just seen hell."