By completing a circuit, the bulb would light up, ignite the TATP and trigger and detonate the chemical mixture in the plastic tubs.Mr Sweeney showed a replica bomb to the jury and said that although six had been made, only five were to be deployed on July 21.'Obviously, these bombs could not be ccde carried on to the public transport system without being hidden from view,' he said.'It was therefore intended to carry each bomb on to the system hidden in a rucksack ccdp carried on the back of the would-be bomber.Since the events of July 2005, scientists from the Forensic Explosives Laboratory in Kent had conducted a number of experiments including explosive tests using a mixture of hydrogen peroxide mixed with ccia chapati flour at a certain ratio.On every occasion this mixture has exploded,' Mr Sweeney told the jury, regardless of whether the scientists used military explosive, a commercial detonator or TATP as the detonator.The jury was ccie played slow-motion footage of some of the explosive tests, which showed the mixture exploding from within a metal tube and a plastic container.Mr Sweeney said the bombs had failed to go off either because the bombers had made too weak a concentration of hydrogen peroxide or because the hot weather had made the chemicals decompose.