7/7 attacks: 'I still think of the man I couldn't help'

It is almost 10 years since the 7/7 attacks on London which killed 52 people.

Three bombs exploded in the Underground network during the morning rush hour and - almost an hour later - a fourth bomb was detonated on a bus at Tavistock Square.

PC Ashley Walker was still in his probationary period with the Metropolitan Police when he saw the explosion in front of him. He ran onto the number 30 to help evacuate the injured and get them treated.