Details of the preparations for a terror campaign, which took place while President Bill Clinton was on a peace mission to the United Kingdom and Dublin, were revealed at the inquest on Edward O'Brien, the terrorist who blew himself up on a bus in central London.
It is believed the information about O'Brien's terrorist activities was found in documents recovered from his flat in south east London.
O'Brien, 21, died on 18 February when the 5lb Semtex bomb he was carrying went off accidentally at the Aldwych.
At yesterday's inquest at Westminster Coroner's Court, in which a verdict of accidental death was recorded, Detective Superintendent William Emerton of Scotland Yard's Anti Terrorist Branch said O'Brien was working for the IRA on the British mainland as early as August 1994.
Police raided O'Brien's flat immediately after the blast and found 33lb of Semtex, 20 timers, four detonators, an incendiary device and ammunition for a 9mm handgun which he was carrying when he died.
They also recovered documents outlining potential future targets.
Mr Emerton said: "It was a complete find of bomb-making equipment which could have sustained a significant bombing attack on the citizens of London."
"I can prove that from August 1994 O'Brien was in London operating on behalf of the IRA and indulging in criminal activity. I can prove that in October and November 1995 he was collecting targeting information and assembling his bomb-making equipment in his flat, clearly intent on carrying out the intentions of the Provisional IRA."
The police are also almost certain that O'Brien was responsible for a planting a Semtex bomb on 15 February in a telephone box in central London, which was later deactivated by the police. An identical sports bag and similar bomb making equipment was found at O'Brien's flat. The inquest heard details of the blast that ripped apart the No 171 bus.
Pathologist Dr Iain West said O'Brien, from Gorey, County Wexford, was killed "virtually instantaneously" by massive injuries caused by the explosion - his legs were blown off, he was peppered with shrapnel, and the force of the detonation ripped his lungs to tatters.
Forensic and pathological evidence suggested that the bomb was being carried in a bag at knee height as O'Brien stood at the bottom of the stairs of the double-decker bus.
Allen Feraday, a forensic scientist, said he could not say exactly why the bomb went off early, but said the most likely reasons included poor training, bad construction, and electrical or mechanical faults.
The inquest was also told of acts of bravery and lucky escapes. PC Miles Manning, who was off-duty when the bomb went off, helped the two passengers and driver injured in the blast. He recalled: "I saw the bus and it looked like there was a huge bite mark where the door should have been.
"Lying in this bite mark was a white male who was still alive and murmuring. Then I looked up and saw the deceased. It was obvious he was dead. His legs had been blown off."