Almost one hour after the attacks on the London Underground, a fourth bomb exploded on the deck of a number 30 double-decker bus, a Dennis Trident 2 was run by Stagecoach London and travelling its route from Marble Arch to Hackney Wick.
Earlier, the bus had went through the King's Cross area as it travelled from Hackney Wick to Marble Arch. At its final destination, the bus turned around and started the return route to Hackney Wick. The bus left Marble Arch at 9:00am and arrived at Euston bus station, the destination, at 9:35am, where crowds of people had been evacuated from the tube and went on buses as a different way of transport.
The explosion at 9:47am in Tavistock Square ripped off the roof and destroyed the back part of the bus. The blast in the explosion took place near BMA House, the headquarters of the British Medical Association, on Upper Woburn Place. A number of doctors and medical staff in or near that building were able to provide immediate emergency help.
People who saw the explosion happen reported seeing "papers and half a bus flying through the air". BBC Radio 5 Live and "The Sun" later reported that two injured bus passengers said that they saw a man exploding the bomb in the bus.
The location of the bomb inside the bus meant the front of the bus remained mostly undamaged from the explosion. Most of the passengers at the front of the top deck remained in the same condition as before, as did those near the front of the lower deck, including the driver, but those at the back of the bus had more serious injuries, with a few people being blown from the bus. The level of the damage caused to the victims' bodies resulted in a longer delay in announcing the death amount from the bombing while the police looked at how many bodies were there and whether the bomber was one of them. A few people nearby the bus were also hurt by the explosion and the surrounding buildings were damaged by debris.
The bombed bus was then covered with tarpaulin and removed so that they could look at the forensics at a secure Ministry of Defence site. The vehicle was later returned to Stagecoach and scrapped on 15 October 2009. A replacement bus, a new Alexander Dennis Enviro400 (fleet number 18500, which has been changed since to 19000, registration LX55HGC), was named "Spirit of London". In October 2012, the "Spirit of London" bus was set on fire in an arson attack. It was repaired at a cost of £60,000 and went back into serving people in April 2013. Two 14-year-old girls were charged for the attack.
The 52 victims were of diverse backgrounds; among them were several foreigners. All the victims were UK residents, including exchange students. Because of train delays before the attacks and transport problems after attacks caused by them, a few victims died aboard trains and buses they would not normally have taken. The victims differed a lot in age, with the youngest being 20 and the oldest being 60 years old, with an average age of 34.
Thirty two victims were British, while one victim each came from Afghanistan, France, Ghana, Grenada, India, Iran, Israel, Italy, Kenya, Mauritius, New Zealand, Nigeria, Romania, Sri Lanka, and Turkey. Three victims were Polish nationals, while one victim was a an Australian born in Vietnam and one held both American-Vietnamese citizenship.
Seven of the victims were killed at Aldgate, six at Edgware Road, 26 at King's Cross and 13 at Tavistock Square.
The four suicide bombers were later found out to be:
All 4 of them were later found out to be connected to Al Qaeda.
Three of the bombers were United Kingdom born sons of Pakistani immigrants; Lindsay was a convert born in Jamaica.
Charles Clarke, Home Secretary when the attacks happened, described the bombers as "cleanskins", a word describing them as previously unknown to the government before their role in the attacks. On the day of the attacks, all four had travelled to Luton, Bedfordshire, by car, then to London by train. They were recorded on CCTV arriving at King's Cross station at about 8:30am.
Two of the bombers made recordings describing their reasons for becoming what they called "soldiers". In a taped broadcast by Al Jazeera on 1 September 2005, Mohammad Sidique Khan, described his motivation. The tape had been edited and mentioned al-Qaeda members Osama Bin Laden, Ayman al-Zawahiri and Abu Musab al-Zarqawi, calling themm "today's heroes". Khan's tape said:
The tape continued:
On 6 July 2006, a recorded statement by Shehzad Tanweer was broadcast by Al-Jazeera. In the video, which may have been edited to include statements and thoughts by al-Zawahiri, Tanweer said:
Tanweer argued that the non-Muslims of Britain deserved to be attacked because they voted for a government which "continues to oppress our mothers, children, brothers and sisters in Palestine, Afghanistan, Iraq and Chechnya."
Early reports suggested that a power surge on the Underground power grid had caused explosions in power circuits, but this was later found out to not be true. Some people suggested that the explanation had been made because of bomb damage to power lines along the tracks that caused power surges. A couple of hours after the bombings, Home Secretary Charles Clarke confirmed the incidents were terrorist attacks.
Although there were safety and police alerts at many areas across the United Kingdom, no terrorist attacks took place outside central London. Suspicious packages were found and removed in areas around the United Kingdom.
"The Times" reported on 17 July 2005 that police sniper units were following many al-Qaeda suspects in Britain. The armed teams were ordered to shoot to kill if there was evidence that suggested that a terror suspect was carrying a bomb and he refused to surrender when asked by police. A person part of the Metropolitan Police's Specialist Firearms Command said that they had been used more often to look at people who might be terrorists.
Vodafone reported that its telephone network reached the most it could at about 10am on the day of the bombings, and it was forced to start emergency plans to put emergency calls first. Other phone networks also said they had problems. The BBC thought that the telephone system may have been shut down by security services to prevent the possibility of mobile phones being used to trigger bombs. This opinion was considered, but it was later found out it was due to a higher amount of texts and calls being made by people. ACCOLC was activated only in a area around Aldgate Tube Station because key emergency personnel did not have mobile phones with ACCOLC. The failures of communication when the emergency was happening caused discussion about how to make London's emergency communications system better.
For most of the day, central London's public transport system was largely out of service following the complete closure of the Underground, the closure of the Zone 1 bus network. The day after the attacks, most London Underground lines would open again, as would most of the Zone 1 buses. In August 2005, it was reported that when public transport opened again it lost 30% of passengers that were travelling before, with more people walking to where they want to go instead of using public transport. Most of the Underground, apart from the stations that were damagedby the bombs, opened again the next morning.
On 2 August, the Hammersmith & City line was reopened but the Circle line was still closed, though all Circle line stations are also served by other lines. The Piccadilly line started serving customers again on 4 August. On 4 August, the Circle line was reopened again.
The first reports about the explosions would come at 9:16am by Sky News, about half an hour after the first explosion. Sky News would also report the final explosion on the bus a few minutes after it happened, with the reporter saying that he believed a bomb had gone off.