At least 50 people have been confirmed dead following explosions that tore through three London Underground trains and a double-decker bus on Thursday 7 July.
Emergency workers and hospital staff responded quickly and efficiently to the blasts, which struck several points on London鈥檚 hectic travel system within the space of an hour. But the co-ordinated attacks injured over 700 people and 22 were still in a critical condition in hospital on Friday.
The first bomb exploded at 0851 BST, aboard a Circle line tube train travelling from Aldgate station to Liverpool Street. Moments later, at 0856 BST, a second explosion tore through a Piccadilly line train travelling deep beneath the ground between Kings Cross and Russell Square. At 0917 BST, another device exploded on a train at Edgware Road in west London. And finally, at 0947 BST, a fourth bomb ripped apart a double-decker bus close to Tavistock Square, in central London.
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Massive investigation
Police and intelligence agencies launched a massive investigation into the attacks, combing through the scene of each explosion and studying CCTV footage for clues as to who may have carried the out the killings.
Speaking at a press conference held in London on Friday, head of the UK鈥檚 anti-terrorist squad Andy Hayman said that each blast was caused by around 4.5 kilograms of explosives. He said devices were apparently placed on the floor of each train and on the floor or the seat of the targeted bus.
But Hayman said the investigation would be affected by the fact that bodies were still being recovered from the tunnel between Kings Cross and Russell Square. 鈥淭here is a risk of the tunnel being unsafe,鈥� he said. 鈥淚t would be wholly unwise and could inhibit a successful prosecution if we rushed this stage.鈥�
Suicide bombers
Eye witness accounts have lead to media speculation that the attack on the double-decker was carried out by a suicide bomber. However, the head of London鈥檚 police force, Ian Blair, said there was 鈥渁bsolutely nothing to suggest this was a suicide bomb鈥�. But he added that: 鈥淭here is nothing to rule it out. It may have been that or it may have been a bomb left on a seat.鈥�
On the day of the attacks, a previously unknown Islamic terrorist group, calling itself the Group of al-Qaeda of Jihad Organisation in Europe posted a statement to a website claiming responsibility. UK home secretary Charles Clarke said the claim had not been verified but was being taken seriously.
Clarke also defended the recent decision to downgrade the terror threat in London, but admitted that intelligence had failed to gather any warning of an imminent strike.
鈥淚t certainly was a failure of intelligence in the sense that we didn鈥檛 know this was coming,鈥� he said. 鈥淏ut by definition when you鈥檙e looking for needles in haystacks you can miss the needles and the tragedy of yesterday is that we did miss the needles.鈥�