They shopped at Currys, Halfords, Tesco and B&Q, buying ordinary items such as gas canisters, lightbulbs, duvets, nails and matches.

The items were usually bought separately and neither the purchases nor the purchasers aroused any suspicion.

But in their garage in Paisley, Bilal Abdulla and Kafeel Ahmed brought these items together to construct crude yet potentially devastating explosive devices, it was alleged yesterday.

Woolwich Crown Court was told that the bombs were to be detonated without warning in busy urban areas to cause maximum loss of life.

The London bombs were hidden by the bedding and packed in two Mercedes saloons parked in the heart of the West End by the two alleged terrorists. Butane canisters were switched on, it was alleged, filling the vehicles with gas. Jerry cans of petrol were opened and the fuel splashed around the interiors.

Hundreds of nails were scattered around which would have made deadly shrapnel had the devices exploded. The explosions were to be set off using mobile-phone detonators, the court was told. Jonathan Laidlaw, QC, for the prosecution, explained to the jury: “Wiring is attached to the buzzer unit of the telephone. When a call is received it sends current to a bulb encased with match heads. The brief flame which would result was to have ignited the air-fuel mixture in the car.

“In error the bombers had allowed the fuel richness of the air within the vehicle to exceed the optimum level for ignition. Put simply, there was not enough oxygen in either car for the petrol and gas to ignite.”

The Glasgow bomb was identical except that Dr Abdulla and Mr Ahmed would set it off themselves using petrol bombs and were prepared to die in the fireball.

Dr Abdulla, the court was told, would admit that he planned a bombing campaign to stage a protest against the treatment of Muslims in Iraq, Afghanistan and Palestine but that it was not intended to kill anyone.

Times Recommends

• Gentleman thief stole pages from rare books
• Picture: the Queen in 1970s flares
• Honoured after 70 years: man who saved thousands