London police have named the third of the attackers who killed seven people in a knife and van attack, and an Italian newspaper says he had been flagged to Britain as a possible militant by Italian authorities.
The fallout from Saturday night's attack has eclipsed other issues in the political campaign ahead of Thursday's parliamentary election, with both the ruling Conservatives and opposition Labour Party battling to defend their records on security.
In particular, the revelation that at least one of the attackers, Khuram Butt, was well known to security services has raised concerns that they lack the resources to prevent attacks.
British police said the third assailant was Youssef Zaghba, 22, and said he had not been a subject of interest for them or the MI5 domestic intelligence agency.
But Italy's Corriere della Sera reported that Zaghba had been stopped at Bologna airport in 2016 when trying to fly to Syria via Turkey, and that Italian authorities had identified him as a potential "foreign fighter" and tipped off Britain about his movements.
Butt, a 27-year-old British national born in Pakistan, had appeared in a British TV documentary called The Jihadis Next Door.
As details about the attackers have emerged, British Prime Minister Theresa May has faced questions about her record overseeing cuts to police numbers when she was interior minister.
Saturday night's rampage, in which Butt, Zaghba and Rachid Redouane drove into pedestrians on London Bridge before slitting throats and stabbing people in the bustling Borough Market area, was Britain's third Islamist attack in as many months.
Less than two weeks earlier, a suicide bomber had killed 22 adults and children at a pop concert in Manchester and, in March, five people died after a car was driven into pedestrians on London's Westminster Bridge.
Police had already named Butt and Redouane, a 30-year-old who claimed to be Moroccan and Libyan. An Italian investigative source said Zaghba was a Moroccan-Italian whose mother lived in the northern Italian city of Bologna.
All three men were shot dead at the scene of the attack by officers within eight minutes of police receiving the first emergency call.
A nationwide minute of silence was held at 11am on Tuesday to honour all the victims.