A man who stabbed two people to death and wounded three others in a "terror-related" attack was shot dead by police on London Bridge after he was held down by members of the public.
Usman Khan, 28, had been released from jail on licence in 2018, half-way through a 16-year sentence for terrorism offences.
Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, were killed in the attack.
Jack Merritt, studied law at the University of Manchester before going to Cambridge to continue his studies.
Saskia Jones, was from Stratford-upon-Avon, Warwickshire, and both were involved in a university prisoner rehabilitation programme at Cambridge University.
Mr Merritt, from Cottenham in Cambridgeshire, was a co-ordinator and Ms Jones a volunteer, the Met Police said.
They were attacked during a conference being held on Friday afternoon at Fishmongers' Hall, at the north end of London Bridge.
The family of Ms Jones paid tribute to her as a "positive influence at the centre of many people's lives".
Ms Jones' former university tutor Colleen Moore told BBC Breakfast: "She was fearless, she was a warrior, she was going to change the world - maybe she will."
"She was a lovely, lovely woman, she made me laugh. She called me out on things - a lot of people were scared of me, she wasn't."
Mr Merritt had a "deep commitment" to the scheme, known as Learning Together, according to people who worked with him.
His father David Merritt said his son was "a beautiful spirit who always took the side of the underdog".
A member of university staff was also among the three people injured.
Two of those, both of them women, remain in a stable condition in hospital, according to police.
Khan's attack began at 13:58 GMT inside Fishmongers' Hall.
Fishmonger Company chief executive Toby Williamson said staff who fought Khan as he launched his attack believed he was wearing a bomb.
He described the scene inside the hall as a game of "pinball bomb with added knives".
He said one staff member in the hall's reception tried in vain to hold Khan back behind doors while another calmly placed a call to emergency services.
Mr Williamson said two men used chairs, fire extinguishers, a pole and a narwhal tusk, which was hanging on the wall, to fend off Khan after he broke through the doors, driving him out of the building.
One of those called Lukasz, a Polish national who was working as a porter in the hall's basement, suffered five wounds to his left-hand side as he fended off the knifeman with a pole during "about a minute of one-on-one straight combat" - allowing others time to escape danger, Mr Williamson said.
Lukasz was taken to hospital for treatment but has since been able to return home.
Khan was forced out of Fishmongers' Hall by a group of men - with hall staff joined by participants of the Learning Together conference - said to include ex-prisoners, probation and prison staff.
Two men can be seen in a video holding the attacker back using a whale tusk, seized from a wall mount, and a fire extinguisher spray, before others stepped in to pin him down.
In a second video a man is seen walking away holding a large knife they had retrieved. British Transport Police said later he was a plain clothes officer.
The Metropolitan Police said its armed officers arrived on the scene within five minutes of the initial 999 call.
The people holding Khan down were moved away by the armed police officers after they thought he was wearing a suicide vest under his jacket.
He was then shot by an officer.
The Met's assistant commissioner said the explosive vest which turned out to be a hoax looked "very convincing".
What do we know about the attacker?
Mr Basu said Khan was released from jail in December 2018.
He had been convicted in 2012 after plotting with a group from Stoke-on-Trent, London and Cardiff.
They discussed attacking the London Stock Exchange and pubs in Stoke, and setting up a jihadist training camp in Pakistan.
One of the conditions of his release was that he should wear an electronic tag.
He also had to take part in the government's desistance and disengagement programme, the purpose of which is the rehabilitation of people who have been involved in terrorism. The Parole Board said it had no involvement in his release from jail.
Usman Khan had spent years preaching in Stoke and had links to the banned organisation al-Muhajiroun.
What is happening now?
An urgent review of the licence conditions of people jailed for terror offences has been launched by the Ministry of Justice (MoJ).
It confirmed the number of offenders convicted of terrorism offences who are currently under supervision in the community is 74.
In a Twitter response to Brendan Cox, whose MP wife Jo Cox was murdered, Jack Merritt's father said: "I obviously don't have full facts about the process that led to the attacker being released but what I can say with certainty is that no one at the event had the slightest inkling that he could or would do something like this.
"We don't need knee-jerk reactions."
Prayers have also been said at Southwark Cathedral for Mr Merritt and Ms Jones.
The Dean, the Very Revd Andrew Nunn, said the incident had brought back memories of the 2017 attack.
Officers have been carrying out two searches; in Stafford where Khan is believed to have lived, and in Stoke-on-Trent.
Mr Basu said police were going through at least 500 images and videos sent to them.
Police patrols across London have been increased as a result of the attack.
The Queen sent "thoughts, prayers and deepest sympathies to all those who have lost loved ones" on behalf of herself and Prince Philip.