Seven people were killed and 48 injured as three men went on a van-and-knife rampage before being shot dead in London Bridge on Saturday.
The killings were the second terrorist atrocity to hit the country in as many weeks after 22 were killed by a suicide bomber at an Ariana Grande concert in Manchester.
Here's what we know about the attack in the capital:
What happened around London Bridge?
The van-and-knife attack saw three men bring carnage to the streets of the capital, ploughing into pedestrians on London Bridge before stabbing revellers with 12-inch knives at nearby Borough Market.
The trio, who wore fake explosive vests, reportedly shouted "this is for Allah" after ditching the vehicle to attack people at bars and restaurants.
Diners had fended the men off with chairs and pint glasses while hundreds fled and took shelter.
This CCTV footage was taken from inside a nearby restaurant as they prevented one of the attackers from entering.
Eight officers fired 50 bullets, described by the Met as an "unprecedented number of rounds", to end the attack.
Both incidents were soon declared by the Metropolitan Police as terror attacks, while a separate stabbing incident at Vauxhall was confirmed as unrelated.
Who were the attackers?
Two of the London Bridge attackers have been named as Khuram Shazad Butt and Rachid Redouane.
Both of the men were from Barking and police said inquiries are ongoing to confirm the identity of the third attacker.
All three were shot dead by armed officers within eight minutes of the first emergency call being made.
Khuram Shazad Butt was a British citizen born in Pakistan.
The 27-year-old was known to the security services, but police said there was no evidence the attack was being planned.
He featured in a Channel 4 documentary 'The Jihadis Next Door'.
Mr Redouane, 30, claimed to be of Moroccan and Libyan origin and was not known to authorities.
He also used the name Rachid Elkhdar and claimed he was 25.
Who has been arrested since the attack?
Several properties in east London have been raided and a dozen arrests have been made since the attack.
Seven women and five men, aged between 19 and 60, were held under the Terrorism Act in Barking on Sunday.
One 55-year-old man was released without charge.
Officers from the Met's Counter Terrorism Command raided two addresses in Newham and Barking in the early hours of Monday and a "number of people" were detained.
The head of the SITE intelligence group said so-called Islamic State claimed responsibility for the attacks.
Who died in the attack?
Canadian national Christine Archibald, the first of those killed to be identified, died in her fiance's arms.
Her grieving family paid tribute to the "beautiful, loving" victim, who had helped at homeless shelters before moving to Europe.
"She had room in her heart for everyone and believed strongly that every person was to be valued and respected," they said.
Canadian Prime Minister Justin Trudeau confirmed her death in what he condemned as a "senseless" attack.
The French Embassy also confirmed a French national died in the terror attack. None of the others killed have been identified.
What do we know about the injured?
The 48 people injured - 21 of whom were left critical - in the van and knife attack were taken to five hospitals.
They included four police officers, several different nationalities and one civilian accidentally shot in the head - but fortunately not critically - when the police opened fire on the attackers.
A British Transport Police officer who took on the three attackers armed with just his baton was stabbed in the head, face and leg as he tried to help members of the public.
Sunday Express business editor Geoff Ho was taken to intensive care after being stabbed while also confronting the attackers near the Southwark Tavern.
"Don't know whether it was stupid or noble to jump in and break up the fight outside the Southwark Tavern," Mr Ho wrote in a Facebook post.
"But two a***s trying to do over the lone bouncer on the door isn't happening on my watch."
The mother of another victim, Daniel O'Neill, said he was approached by a man who said "this is for Islam" before sticking a knife in him.
Elizabeth O'Neill said her 23-year-old son has got a seven-inch scar "going from his belly round to his back".
Seven French nationals - in addition to the nation's citizen who died - were taken to hospital, of which four are in a serious condition.
Four Australians, a New Zealander and two Germans were also hurt.
The Metropolitan Police has opened a casualty bureau for anyone concerned about friends or relatives who may be affected on 0800 096 1233 and 020 7158 0197.
What has the political reaction been?
Prime Minister Theresa May said the UK was experiencing a "new trend in the threat we face as terrorism breeds terrorism".
She condemned the terror attacks - saying "enough is enough" - after chairing a meeting of the Government's Cobra emergency committee on Sunday morning.
National campaigning in the General Election was suspended for a day, though Ukip continued to campaign, but Mrs May confirmed the General Election will go ahead as planned on Thursday.
Speaking in Downing Street, she urged the public to "go about their lives as they normally would".
Labour leader Jeremy Corbyn called the attacks in London "brutal and shocking", while Lib Dem leader Tim Farron said the government needed to pledge to invest more in police and security services.
"Theresa May said enough is enough, but enough was enough the first time around," Mr Farron said.
Meanwhile, London Mayor Sadiq Khan described the incident as "deliberate and cowardly".
US President Donald Trump spoke to Mrs May to offer his condolences for the "brutal" terror attack, the White House said.