Boris Johnson and Jeremy Corbyn are among those expected to attend a vigil for the victims of the London Bridge attack in the capital later.
Jack Merritt, 25, and Saskia Jones, 23, will be honoured in a remembrance service at Guildhall Yard in the City.
They were stabbed to death by convicted terrorist Usman Khan, 28, at a prisoner rehabilitation event on Friday.
It comes amid an urgent review of the licence conditions of convicted terrorists released from prison.
A book of condolences will be opened at Guildhall Art Gallery, and members of the public will be invited to lay flowers outside nearby Mansion House.
The service will take place at 11:00 GMT, less than a mile from Fishmongers’ Hall, where Usman Khan launched his attack on Friday.
Khan, who was released from prison in December 2018 after serving half of his sentence, was later shot dead by police on London Bridge.
Prime Minister Boris Johnson said on Sunday that 74 people jailed for terror offences and released early will have their licence conditions reviewed.
Later that day, Staffordshire Police said a 34-year-old man had been arrested on suspicion of preparation of terrorist acts – but added there was no information to suggest the man was involved in the London Bridge attack.
Mr Merritt and Ms Jones were both University of Cambridge graduates, and had been attending an event for the university’s Learning Together programme – which focuses on prisoner rehabilitation – when they were attacked.
Their families have paid tribute to their loved ones.
Ms Jones’ family said their daughter, from Stratford-upon-Avon in Warwickshire, had a “great passion” for supporting victims of criminal justice.
“Saskia was a funny, kind, positive influence at the centre of many people’s lives,” the family statement read.
“She had a wonderful sense of mischievous fun and was generous to the point of always wanting to see the best in all people.
“She was intent on living life to the full and had a wonderful thirst for knowledge, enabling her to be the best she could be.
“This is an extremely painful time for the family. Saskia will leave a huge void in our lives and we would request that our privacy is fully respected.”
In a statement, Mr Merritt’s family described him as a “talented boy” who “died doing what he loved”.
“Jack lived his principles; he believed in redemption and rehabilitation, not revenge, and he always took the side of the underdog.
“Jack was an intelligent, thoughtful and empathetic person.
“We know Jack would not want this terrible, isolated incident to be used as a pretext by the government for introducing even more draconian sentences on prisoners, or for detaining people in prison for longer than necessary,” the statement read.
Cambridge University’s vice-chancellor said he was “devastated to learn that among the victims were staff and alumni”.
Prof Stephen J Toope said: “What should have been a joyous opportunity to celebrate the achievements of this unique and socially transformative programme, hosted by our Institute of Criminology, was instead disrupted by an unspeakable criminal act.
“Among the three people injured, whose identities have not been publicly released, is a member of university staff.
“Our university condemns this abhorrent and senseless act of terror.”
Speaking to the BBC, Prof Toope said the fact Mr Merritt was killed by someone he was trying to help “is the greatest tragedy of all”.
“I have profound sadness for the family,” he added.
London Bridge itself, which was cordoned off for most of the weekend to allow forensic work to be carried out, has been reopened to traffic, although there remains a heavy police presence in the area.
Toby Williamson, chief executive of Fishmongers’ Hall, praised the bravery of his staff who intervened to stop the attacker, hailing their actions as “extraordinary things done by ordinary people”.
Among them was Polish chef Lucasz, who was working as a glass cleaner in the basement of the hall.
Mr Williamson told how Lucasz suffered five wounds to his left-hand side as he fended off the knifeman with a narwhal tusk during “about a minute of one-on-one straight combat” – allowing others time to escape danger.
Two others grabbed makeshift weapons such as fire extinguisher before the attacker fled down a staircase before getting trapped in reception.
Flower tributes were placed near the bridge, with one reading: “”I love you forever I am so proud of you.”
Another dedicated to victim Jack Merritt read: “Rest in peace Jack. You were a wonderful friend to us.”
Prime Minister Boris Johnson, Labour leader Jeremy Corbyn and the Mayor of London Sadiq Khan are expected to be among those at the vigil at Guildhall Yard in the City of London for the victims of the attack.
It follows a service for the victims on Sunday at Southwark Cathedral, which was attended by hundreds of people.
Dr Vin Diwaker, medical director for the NHS in London, said two people injured in the attack remained in a stable condition in hospital, while one had been able to return home.
Friday’s attack comes after the UK’s terrorism threat level was downgraded on 4 November from “severe” to “substantial”, meaning that attacks were thought to be “likely” rather than “highly likely”.
The terror threat level is reviewed every six months by the Joint Terrorism Analysis Centre, which makes recommendations independent of government.
Eight people died and 48 were injured by three men who drove into pedestrians, then stabbed people in Borough Market, in London Bridge in 2017.