On Saturday June 3, a van mounted the pavement and mowed down pedestrians on the bridge, before three attackers, armed with knives, began stabbing people near Borough Market.
The three attackers, who were shot dead, have now been identified by police, and one of them, Rachid Redouane, lived in Harrow when he first arrived in Britain in 2006.
What do we know about the terrorists so far?
The first clue to Redouane's background came when authorities found an Irish identity card on the body of one of the suspects, after they were shot dead by police on the scene.
Redouane, 30, who was based in Barking before the attack, claimed to be Moroccan-Libyan and also went by the name Rachid Elkhdar, claiming to be six years younger.
After settling in Harrow, he reportedly applied for asylum in the UK, but the application was rejected in 2009.
It is not clear when he arrived in Ireland or how long he stayed but it is believed he used Irish jurisdiction to get a European Union permit which later allowed him to be in the UK.
Security sources in Ireland confirmed he married a British woman in Dublin in 2012 and lived in Rathmines, Dublin.
The marriage reportedly allowed him to obtain a 4 EU FAM card given to spouses of European Union citizens.
Redouane left Ireland after the wedding and may have travelled to Morocco before settling in the UK.
He returned to Ireland in 2015, again for an unknown length of time, but Taoiseach Enda Kenny said he was not one of a small number of radicals under surveillance.
An Irish security source described the killer as having "extensive immigration history related to the UK".
Redouane, reportedly a former pastry chef, is said to have had a 17-month-old daughter with his wife, although the couple were estranged.
According to reports he visited his child in the hours before the attack.
Khuram Shazad Butt
A 27-year-old Pakistan-born British citizen who was known to police and MI5 and was the subject of a 2015 investigation.
He is alleged to have been an associate of jailed hate preacher Anjem Choudary and appeared in the 2016 Channel 4 Islamic extremist documentary The Jihadis Next Door.
The Jabir Bin Zayid Islamic Centre, where Butt occasionally worshipped, said he was once asked to leave "after interrupting a Friday sermon".
Mohammed Shafiq, chief executive of anti-extremism group the Ramadhan Foundation, said Butt called him a "Murtad" - traitor in Arabic - when he confronted Choudary about supporting terrorism days after the 2013 murder of Lee Rigby.
Residents at a block of flats in Barking, east London, where several arrests were made on Sunday, said Butt, known locally as "Abs" or "Abz", had lived in the area for around three years.
The father of two young children was a keen gym-goer and weightlifter, neighbours said.
Butt worked out at the Ummah Fitness Centre in Ilford, where a message on the door said: "While Mr Butt did occasionally train here at UFC gym we do not know him well nor did we see anything of concern, we will of course help the police in any way we can."
Police said Butt had appeared on the radar of security services but was in "the lower echelons of our investigative work".
He was reported to counter-terrorism authorities in July last year after a "violent scuffle" with a member of an anti-extremism organisation.
He rowed with the Quilliam Foundation's Dr Usama Hasan at a June event to mark Eid, the end of Ramadan, which turned violent after others intervened, the organisation said.
A 22-year-old Italian national of Moroccan descent was living in east London and reportedly worked in a Pakistani restaurant in Ilford.
The Corriere della Sera newspaper said Fez-born Zaghba's Italian mother lived in the northern city of Bologna, having parted from his father and left their Moroccan home.
It was reported that he was stopped by Italian police in March last year at Bologna's airport trying to get to Syria via Turkey, and that this was communicated by Italian intelligence to their UK counterparts.
Scotland Yard said he was not a police or MI5 "subject of interest", despite Italian media reports.
Authorities ruled there was insufficient evidence to accuse him of terror-related crimes.
He was placed on a watch list but his phone and passport were returned to him, allowing him to come to the UK.
The opening of the roads came as police carried out a search warrant at an address in east London in the early hours of Wednesday (June 7).
Officers from the Met’s Counter Terrorism Command, supported by officers from the Territorial Support Group, entered the address in Ilford at around 1.30am.
A 30-year-old man was arrested on suspicion of the commission, preparation or instigation of terrorist acts (contrary to section 5 Terrorism Act 2006) and has been taken into custody at a south London police station under the Terrorism Act 2000.
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