The bomb, made of 12.5kg (28lbs) of Semtex, would have brought the roof down on an audience of 300 people at the Becks Theatre in Hayes, west London.
John Bevan, for the prosecution, said 'it was simply a miracle' that the bomb, which was left in a holdall by the stage door, did not go off. He said the bomb, which had a one-hour timer, failed to explode because of a faulty microswitch.
A brown bag in the holdall containing the bomb bore 37-year-old Mr Canning's fingerprints, the court was told. Also in the holdall was a bin liner allegedly bearing the fingerprint of Ethel Lamb, 60, Mr Canning's lover.
Mr Bevan said the prints proved Ms Lamb's complicity in the bomb-making, probably at the home she shared with Mr Canning in Northolt, west London.
Ten months after the bomb was planted in June 1991, the two were arrested and the match with their fingerprints made. If the bomb had exploded, all trace of their involvement would have been destroyed, the court was told.
They deny conspiracy to cause explosions and possessing Semtex with intent to endanger life and damage property and possessing six Kalashnikov rifles.
The hearing continues today.