It could have been worse on July 7. From the TimesOnline, :
After examining all the possible reasons why the bombers left bomb-making components in the boot of a car at Luton railway station, investigators consider it likely that the four terrorists had intended to build devices with at least 20lb of home-made explosives.
The suggestion that the explosives, nails and other components found in the red Fiat had been left there for a follow-on terrorist team has been discounted. One possibility is that their rucksacks were too small for bigger devices.
The theory emerged as three Iraqis were questioned by detectives yesterday after being arrested taking photographs near to the venue for a European Union foreign ministers” meeting next week, near Newport, Gwent. The men were held under the Terrorism Act 2000.