Investigators in London are sifting through the forensic evidence left at the scene after yesterday’s attempted bomb attacks. Once again three underground trains and a bus were targeted but unlike on July 7 it is thought the devices only partially exploded, with perhaps just the detonators going off.Why they failed is unclear. But whether it was down to poor construction, old explosives or other factors, the city’s police chief is in no doubt the intention was to kill. Eyewitnesses described hearing bangs but unlike the calm seen two weeks ago, there was desperate panic at some underground stations. The strikes happened at Warren Street, the Oval and Shepherd’s Bush stations and on the Number 26 bus on the Hackney Road. At the Oval passengers said when the train stopped a man ran away, despite attempts to stop him. Just one person was hurt, unlike the carnage of July 7, when 56 people died and hundreds more were injured. And this time police have a wealth of evidence – the unexploded devices and the rucksacks they were carried in, plus footage from security cameras. A man arrested in Downing Street yesterday remains in custody but it is not clear if the incident is linked to the blasts.