On Saturday, June 3, Khuram Butt, Rachid Redouane and Youssef Zaghba drove a hired van into pedestrians on London Bridge before stabbing people in the area around Borough Market. But the warning about the 22-year old who helped kill eight people and injure 48 more on Saturday night appears not to have been picked up.
London mayor Sadiq Khan has also urged the police and security services to answer questions as to why they did not act on prior warnings about Butt's behavior.
Butt was a British citizen who was born in Pakistan, London's Metropolitan Police said.
The security and intelligence services and police have stopped 18 plots since 2013, including five since the Westminster attack, Mr Rowley added. His mother, Valeria Collina, 68, said he had become friends with Butt and the third attacker, Rachid Redouane, 30. The terror attack claimed the lives of 7 innocent bystanders and injured around 50 others.
Authorities also carried out two additional search warrants in east London, police said.
Butt was reported to anti-terror police over fears he was attempting to radicalise schoolchildren, according to reports.
Transport for London has confirmed that Butt worked as trainee customer services assistant for six months previous year.
Italian security sources have revealed that Britain is home to at least 100 other Italians who have been flagged as posing a potential terrorist risk on the same Europe-wide database that Zaghba appeared on.
He had been notified to British and Moroccan authorities by Italian intelligence when Italian police intercepted him on 15 March 2016 at Bologna Airport with a one-way ticket for Istanbul, two officials said on condition of anonymity.
The call from the leader of Australia's opposition party echoed sentiments expressed by the nation's Prime Minister Malcolm Turnbull, who said Monday that social media companies need to be more vigilant in policing content.
Relatives of Australian Sara Zelenak have confirmed she was killed in the London attacks over the weekend.
Butt, 27, was a British citizen born in Pakistan who was known to security services, while Italian authorities said they warned the United Kingdom that 22-year-old Zaghba was a "possible suspect".
Collina said she told her son, "At this point you should be flawless".
"It is now clear that, sadly, victims came from a number of nationalities".
May said all three attackers in Saturday's attack have been identified, and that when "progress in the investigation permits", their names will be released. "And this is the result, what we see happen on London Bridge".
Further to Geraghty's point about "permanently nonviolent radicals", here's counterterror expert Maajid Nawaz on Fox this morning warning that the same jihadi who appeared on the TV show also attacked a member of his staff previous year - and that police knew about it.
During that time, police numbers have dropped by roughly 20,000 officers, and the number of armed officers has fallen as well.