On the morning of 7 July 2005, London was celebrating after beating Paris in the race to host the 2012 Olympics.
The four bombers arrive at Luton to catch a train
But within hours, the euphoria had evaporated as four suicide bombers killed 52 passengers and injured nearly 800 on the city's transport network.
Here is how the day unfolded:
0715 BST: Four young British Muslim men, all carrying large rucksacks, enter Luton train station, in Bedfordshire.
Mohammad Sidique Khan, 30, Shehzad Tanweer, 22, Hasib Hussain, 18 - who have all driven together from Leeds that morning - and 19-year-old Germaine Lindsay look like they are heading off on a camping trip, but each rucksack contains an estimated 2-5kg of high explosive.
0725: The four men mingle with the suited commuters on a train to London King's Cross Thameslink.
0830: CCTV images at King's Cross station appear to show the four men hugging and in a happy mood. They then split up, each one apparently going towards a different section of the London Underground.
0850: Shehzad Tanweer sets off his bomb between Liverpool Street and Aldgate stations on the eastbound Circle Line. Tanweer's bomb kills seven people and injures 171.
Mohammad Sidique Khan, on board a westbound Circle Line train, fiddles with his rucksack before it explodes at Edgware Road, killing six other people and injuring 163.
Germaine Lindsay is on a packed Piccadilly Line train as it travels between King's Cross and Russell Square. The blast from his rucksack kills 26 other people and leaves more than 340 injured.
0852: London Underground reports power surges on the underground network - it is the effect of the simultaneous explosions but LU control does not know this yet.
0855: Hasib Hussain is seen on Euston Road, outside King's Cross station. He tries to contact his friends on a mobile phone. He gets no reply.
0900: Hussain goes back into King's Cross mainline station, where he buys a 9-volt battery from WH Smith before heading across Euston Road to McDonald's.
0915: Emergency services confirm they have been called to Liverpool Street station after reports of an explosion. A power failure may be the cause, Transport for London says.
London Underground has received reports of a train derailment at Edgware Road, a person under a train at Liverpool Street and walking wounded leaving stations.
It begins shutting down the entire network and evacuating an estimated 200,000 passengers from more than 500 trains.
0919: A man fitting Hasib Hussain's description is seen looking nervous and pushing past people on a number 91 bus from King's Cross to Euston station, where he switches to the number 30 bus travelling east from Marble Arch.
0929: The Metropolitan Police confirm they are dealing with a major incident in London, but say it is too early to know what has happened.
0930: Cabinet Office Briefing Room A (Cobra), the government's national crisis management facility, is activated to co-ordinate the response to the unfolding events.
0940: British Transport Police say power surges have happened on the underground at King's Cross, Edgware Road, Russell Square, Aldgate and Old Street.
0947: The number 30 bus is crowded because of the Tube closures, but Hasib Hussain finds a seat on the upper deck towards the back.
Hussain's device goes off in Tavistock Square - killing 13 other people and injuring more than 110 - nearly an hour after those of his friends.
Hussain may have decided not to board a Northern Line Tube train from King's Cross because of delays, or was possibly unable to detonate his device with the original battery.
0955: BBC News website readers begin e-mailing their accounts and pictures of what is happening in London.
0957: Andrew McCormack e-mails: "My gf works up by holborn and has just called to tell me a bus has exploded outside her office in tavistock square, bodies strewn all over the road."
Jolyon Segal's e-mail says: "I have just managed to travel into work via taxi, having seen people injured and looking dazed on the tube. It's mayhem and no-one knows what is going on - rumours already abound of terrorist attack and deaths."
1021: Scotland Yard says there have been "multiple explosions" in London and two minutes later BTP confirm there has been an explosion on a bus in Tavistock Square.
1040: All London hospitals are on major-incident alert.
1053: Home Secretary Charles Clarke says "dreadful incidents" have caused "terrible injuries".
1118: London's Metropolitan Police Commissioner, Sir Ian Blair, says he knows of "about six explosions" but it is "still a confusing situation".
1125: The first reports confirming deaths in the blasts emerge. A police spokesman says there are at least two fatalities.
1205: Prime Minister Tony Blair, breaking off from the G8 summit in Gleneagles, says there has been "a series of terrorist attacks in London... there are people that have died and people seriously injured".
1210: A website linked to al-Qaeda carries a statement saying it has carried out a "blessed raid" in London "in retaliation for the massacres Britain is committing in Iraq and Afghanistan".
1255: Mr Clarke tells MPs four explosions have been confirmed, three on trains and a fourth on a bus, but it is not known who is responsible.
WHAT HAPPENED NEXT
9 July 2005: Police teams find more evidence of the bombers' identities
12 July: Premises in West Yorkshire searched. These include the Leeds flat where bombs were made
14 July: Police publicly name Tanweer and Hussain
16 July: Khan and Lindsay named as other bombers
27 July: Pictures emerge of bombs left behind by the bombers in a car at Luton
1 September: Al-Jazeera TV releases video of Khan justifying such attacks
19 September: Al-Qaeda's deputy leader says it "launched" the attacks
11 May 2006: True extent of al-Qaeda involvement remains unclear, government says
11 May: MPs' report says lack of resources prevented security services intercepting bombers
6 July: Video released showing Tanweer saying the attacks were "only the beginning"
1313: The Mayor of London, Ken Livingstone, says Londoners responded "calmly and courageously" to the "cowardly terrorist attack".
1458: Sir Iqbal Sacranie, secretary general of the Muslim Council of Britain, joins other religious leaders in condemning the attacks.
1525: Fears of a substantial death toll are confirmed when police reveal that at least 33 people have been killed. Some of the seriously injured have lost limbs.
1635: The union jack flying over Buckingham Palace is lowered to half mast at the Queen's request.
1732: Mr Blair says the "slaughter of innocent people" through terrorism will not intimidate Britain.
"When they seek to change our country, our way of life by these methods, we will not be changed. When they try to divide our people or weaken our resolve, we will not be divided and our resolve will hold firm."
1813: The number of confirmed dead rises to 37.
1940: The attacks bear all the hallmarks of al-Qaeda, says Foreign Secretary Jack Straw. He adds that neither the British police nor the intelligence services had any warning of the attacks.
2219: The emergency casualty bureau receives a call from the family of Hasib Hussain, reporting him missing.
2340: A police exhibits officer tells investigators that cash and membership cards in the names of "Sidique Khan" and "Mr S Tanweer" have been found at the scene of the Aldgate blast. Police are on the trail of the bombers.
Seven killed, 171 injured between Liverpool Street and Aldgate
Six killed, 163 injured at Edgware Road
26 killed, 340 injured between King's Cross and Russell Square
13 killed, 110 injured on bus in Tavistock Square
In addition, one bomber died in each attack