Old and unstable bomb killed terrorist

The IRA bomb that accidentally detonated on a bus in central London, killing the terrorist carrying it, went off because it was an old device that had been badly maintained, police have concluded.

Commander John Grieve, head of the Anti-Terrorist Squad, is expected to reveal this today at the inquest into the death of the bomber, Edward O'Brien. He will also disclose that O'Brien, contrary to earlier reports, was not an inexperienced "lilywhite", but a hardened terrorist responsible for several other attacks.

It is also understood that all the film from the closed-circuit camera fitted on the No 171 double decker was destroyed during the explosion at the Aldwych. Until now, it has remained a mystery as to whether the Anti Terrorist Branch had pictures of O'Brien and any other IRA operatives boarding the bus, which was reduced to a pile of twisted metal when the 5lb Semtex bomb detonated at 10.30pm on 18 February.

Security sources believe O'Brien, 21, may have been intending to target the nearby Law Courts. Cdr Grieve is expected to tell the inquest, which reopens at Westminster Coroner's Court, that the bomb was almost certainly one left over from the previous IRA bombing campaign, and was probably about three years old.

Fragments of the device found scattered around the wreckage indicated that the device was old and badly maintained, making it very unstable. Anti terrorist officers also recovered O'Brien's handgun close to the bus.

Anti terrorist officers were able quickly to find O'Brien's flat in Lewisham, south-east London, through documents discovered on his body. Enough Semtex and bomb-making equipment were found at his home and buried in the garden to make a further 20 devices.

The bus explosion was the third of four IRA attacks that have taken place since the 17-month ceasefire was broken in February by the huge Docklands bomb. Cdr Grieve is known to be satisfied with the progress of the investigation into the Docklands bombing. It was revealed in the Independent on Sunday that several witnesses who may be able to identify the terrorists have been found by anti terrorist officers. Some are on the fringes of the East End underworld and spotted the bombers in the final stages of their mission.