Muslim schoolgirls, police officers, faith leaders and tourists were among thousands of people who joined hands on Westminster Bridge in a show of defiance a week after a terror attack that killed four people.
The vigil came before crowds held an 82-second silence at 2.40pm, to mark the time Khalid Masood launched his massacre.
Nurses and doctors from St Thomas' Hospital, where many of the injured were treated, joined those on the bridge, alongside police officers and members of the emergency services.
Rain began to fall as the crowd fell silent in the shadow of the Palace of Westminster, before dozens of people laid flowers near the site of the attack and along the bridge.
One of more than 35 victims injured when Masood ploughed his car into pedestrians was pushed in a wheelchair to lay a tribute to the four people killed in the rampage.
Craig Mackey, Acting Commissioner of the Metropolitan Police, told mourners: “This afternoon is about remembering the victims of last week's events.
“Our thoughts, our prayers, go out to everyone who was affected by the events last week.
"I would urge you, if you get time, to go on to the bridge, talk to Londoners, talk and get a feel for this great city and how it's come together in responding to these events."
Organisers of the Hands Across Westminster Bridge memorial said they wanted to show that London would not be divided by the atrocity, linking “all nations, faiths, orientation and sexes”.
More than 500 faith leaders from across Britain walked across the bridge together as part of the memorial, the Metropolitan Police Federation said.
School pupils aged nine and 10 from the Al-Sadiq and Al-Zahra Schools clasped yellow roses and held signs reading "Islam says no to terror" and "please don't kill innocent people" as they walked across the Thames.
Hundreds of members of the Ahmadiyya Muslim Youth Association were on the bridge, wearing T-shirts with the message "I am a Muslim, ask me anything".
Zafir Malik, an imam from the association, said they were invited by police and wanted to "show that what happened here last week had nothing to do with the so-called religious aspect that this has been given".
"[It has] nothing to do with Islam, nothing to do with what we believe in and preach on a daily basis,” he added.
“We're here to show that we are united with our fellow countrymen and remembering those who have fallen, especially PC Keith Palmer. We are here and showing our solidarity for the country.”
Members of the Ahmadi Muslim community also carried banners reading “love for all and hatred for none” as part of a campaign similar to that seen after the Berlin attack.
Westminster Bridge was closed for the event, having reopened just a day after the attack and been adorned with floral tributes to the victims, was closed to traffic.
Vigils were also held across the country to coincide with the Westminster event, and a separate minute’s silence was held by the Metropolitan Police around the eternal flame at New Scotland Yard.
The death and carnage wreaked in 82 seconds of terror was detailed as inquests opened into the victims’ deaths at Westminster Coroner's Court on Wednesday.
He then crashed into railings outside the Houses of Parliament, ran into an entrance and stabbed PC Keith Palmer to death, before being shot dead by armed police.
Officers continue efforts to establish the motive of Masood, a 52-year-old Muslim convert who had a lengthy criminal history and lived in areas including Sussex, Birmingham and London.
Isis hailed him as a “soldier of the Islamic State” in its claim of responsibility for the attack but the extent of the group’s involvement remains unclear.
Twelve people have been arrested in connection with the probe but only one remains in custody - a 30-year-old man suspected of preparing terrorist acts.
A 32-year-old woman from Manchester been released on bail and 10 others arrested were freed with no further action.
Additional reporting by PA