The Daily Mirror's headline sums up what many are asking on Tuesday, "So how the hell did he slip through?" referring to Khuram Butt, one of the three London Bridge attackers.
He is pictured in several papers unfurling a black flag associated with so-called Islamic State, on a Channel 4 documentary screened last year.
He was, says the Daily Telegraph - the brazen jihadist who was free to parade his extremism on TV, and yet the police concluded he was not a threat.
"We had him - and let him go" is the headline in the Daily Mail, picking up on what it calls a "shocking admission" from Scotland Yard and MI5.
The Times reports that Butt was deemed a "low priority", despite being linked to a key contact of one of the 7 July suicide bombers in 2005. It believes his extremist links will pile pressure on police and MI5, who are already facing scrutiny over their failure to prevent three atrocities in Britain in 10 weeks.
"Evil in plain sight" is a headline in the Sun. The paper profiles another of the killers, Rachid Redouane, who it says is believed to have been radicalised during a trip to Morocco where he was born. According to the Sun, he had split up with his partner, and mother of his baby daughter, in January after she had become sick of his Islamist and homophobic views.
The Guardian highlights a warning by the UK's top counter-terrorism officer, Mark Rowley, that the country will need to radically reform its strategy to stop jihadi attacks because the threat is now at a "completely different" level of danger.
A photograph in the Daily Express shows hundreds of commuters walking over London Bridge on Monday morning as they returned to work following the attack. It was - the paper says - the day London marched on in defiance.
The Times describes how one of the victims on Saturday, James McMullan, had been in celebratory mood on the night he died after working for 16 hours a day to create a business that he hoped would revolutionise online education.
The paper says he was an entrepreneur who had gained a £1.2m investment for his business.
The 'I' newspaper focuses on what it calls an "inspirational message" from Mr McMullan's family and their vow that "we will not be dragged into hatred".
As the general election campaign enters its closing stages, the Labour leader, Jeremy Corbyn uses an interview in the Guardian to hit back at Theresa May's attempt to portray him as "unpatriotic" and "soft on terror".
He dismisses the claim as "utterly ridiculous and offensive".
The Prime Minister tells the Telegraph that if she's re-elected, she would consider giving the government new powers to block access to extremist websites if internet companies failed to act over online radicalisation.
There are many warm tributes to actor Peter Sallis, who found fame as the mild-mannered Clegg in Last of the Summer Wine and was the voice of Wallace in the Oscar-winning animations, Wallace and Gromit.
The Mirror describes Sallis - who has died at the age of 96 - as a "sitcom icon" who grew old on screen without ever growing up, "he aged like a vintage wine".
The Times' obituary says his nasal voice was compared to a pair of warm slippers in an uncertain world.