A minute's silence was kept, and candles were lit both on the steps at Trafalgar Square, and in a bank among the crowds. While many people left quickly after Thursday evening's 15-minute vigil, others stood silently in the usually noisy square, holding candles or gazing at those on the steps. Surrounding streets had been blocked off and were empty of traffic.

"I wanted to be with people who wanted to remember what happened yesterday, and to make a message of strength. I was very upset yesterday - there's something about it being in the heart of your home," Lauren, a therapist who preferred not to give her last name, told DW.

Londoner Keith Evans was moved by the event, which gave him a sense of closure he didn't have after the July 7, 2005 bombings, the worst terrorist attack on London in recent memory until Wednesday's incident.

"I was abroad when 7/7 happened, so I wanted to come to show my feelings," Evans said. "It's quite moving, the minute's silence."

'Terrorists will never succeed'

Police have so far named three of the four people who died, along with the attacker: Police Constable Keith Palmer, 48, American Kurt Cochran, 54, and Aysha Frade, 43, a British national of Spanish and Cypriot origin. 

Cochran and Frade were killed when Khalid Masood drove his car into pedestrians on Westminster Bridge before crashing into the railings of the Houses of Parliament, and then knifing PC Palmer, who was unarmed.

Home Secretary Amber Rudd and London Mayor Sadiq Khan addressed the heavily policed crowds Thursday evening.

"We are strong in our values and proud of our country," Rudd said.

Khan said Londoners would "never be cowed" by terrorism. "Those evil and twisted individuals who try to destroy our shared way of life will never succeed," he told the crowd. 

Questions about security

While CCTV cameras leave criminals almost nowhere to hide in the United Kingdom, this week's terrorist incident has raised questions among worried citizens about armed police - an uncommon sight in the isle-nation.

Spanish journalist Meritxell Vallve, who has lived in London for seven years, said the collective response was too understated.

"The English are too proud of themselves saying: 'We will never be defeated.'" Having lived in San Francisco in 2001 and seen the military presence there after the 9/11 atrocities, she said there should be "more police, more of them armed, especially by landmarks, to protect tourists."

However, others said the police response on Wednesday reflected a well-functioning system in a city already on alert for terrorist attacks for over 10 years.

Nestor, who works in the National Gallery adjacent to Trafalgar Square, said arming all officers could actually undermine public safety. "People who want to do harm just grab it and use it," he told DW, referring to last Saturday's attack in Paris' Orly airport, in which the officer was carrying a gun.

Muslim community 'somber,' on edge

"As a Muslim today I'm proud to be a Londoner," said Indian-born Sultan Campwala, who has lived in the city for 15 years and attended the vigil. "Myself and loads of my friends have made special prayers in the mosque for the people who died and for the safety of this country."

Behind the speakers stood representatives of the city's many faith communities. Rabbi Nathan Levi of the London Faiths Forum, said: "There's already been a backlash that we're hearing about, from mosques around the country - people pulling hijabs, people pulling people's beards; in Birmingham, people trying to get into a mosque. After an event there's always a fear that things will get much worse."

He continued: "In the Jewish community at least there is a trail that Muslims don't stand up and speak for peace in these moments, so by being together we amplify all of our voices. Oftentimes it's not that they're not speaking, it's that they're not being heard."

Yasmeen Akhtar, of the Three Faiths Forum, described the mood across Britain's roughly 3 million-strong Muslim community as "somber."

"Not only are they experiencing the fear and concern as regular citizens, there's a backlash they unfairly experience because of the way these things are reported," Akhtar said.

The flags of government buildings, embassies and Westminster Abbey remained at half-mast in honor of those who had died. The Houses of Parliament were closed to all but passholders - MPs and peers - and Westminster Abbey said it was open for prayer but closed to tourists. A minute's silence was observed at 9:33 a.m. in honor of the police officer, Keith Palmer, whose shoulder number was 933. Well-wishers left flowers by the cordons at the National Police Memorial in honor of PC Palmer, and on Westminster Bridge, and earlier, by the cordons that kept the location of yesterday's horror sealed off.

This is an updated version of a previous article.