On 22 March 2017 a terrorist attack in London began on Westminster Bridge, and continued into Parliament Square and the grounds of the Palace of Westminster.
The attacker, identified as 52-year-old Briton Khalid Masood, drove a car into pedestrians on the pavement along the south side of Westminster Bridge, resulting in more than 50 people being injured, three of them fatally.
After the car crashed into the perimeter fence of the Palace grounds, he abandoned it and ran into New Palace Yard where he fatally stabbed an unarmed police officer.
Prior to the attack, the UK Threat Level for terrorism in the country was listed at "severe", meaning an attack was "highly likely".
The last terrorist incident that occurred at the Palace of Westminster was the assassination of Airey Neave in 1979, during the Northern Ireland conflict.
At around 14:40 local time (and UTC) on 22 March 2017, a grey Hyundai car was driven at speed into pedestrians (including three police officers) along the pavement on the south side of Westminster Bridge, causing multiple casualties.
The car used was hired from Enterprise Rent-A-Car in Birmingham during the week prior to the incident.
One of the victims fell or was thrown by the car's impact over the parapet of the bridge into the River Thames below.
Masood, wearing black clothes, got out of the car and ran around the corner into Parliament Square and through the Carriage Gates of New Palace Yard, part of the Palace grounds, where he fatally stabbed an unarmed police officer, PC Keith Palmer.
Sitting in a car nearby was a Metropolitan Police close protection officer for the Secretary of State for Defence, Sir Michael Fallon.
Upon witnessing the stabbing, the officer proceeded to run towards the scene, where he shot Masood several times.
Passers-by including Tobias Ellwood MP, Foreign Minister for the Middle East and Africa, and medics attempted to revive PC Palmer, also without success.
As this was happening, Prime Minister Theresa May, who was in the Commons for a vote, was evacuated by her security team, in the Prime Ministerial car, and taken to 10 Downing Street.
It was the first terrorist attack in London since the murder of Lee Rigby in May 2013[dubious – discuss] and caused the most casualties of any attack in the UK since the 7 July 2005 London bombings.
Parliamentary staff were told to remain in their offices, and visitors to Parliament, including journalists and children on school trips, were ordered to remain in the building.
The Scottish Parliament and the National Assembly for Wales also suspended their proceedings on the afternoon of 22 March.
The UK government's emergency Cabinet Office Briefing Room (COBRA) committee, chaired by the Prime Minister, met in response to the attack.
Five people, including the perpetrator, died as a result of the incident, and around 50 others were injured, some of them severely.
Aysha Frade, a British woman of Spanish and Cypriot ancestry, believed to have been walking along the bridge to pick her children up from school, was struck by the perpetrator's car and killed.
The dead police officer was PC Keith Palmer, 48, an unarmed police officer who was on duty with the Parliamentary and Diplomatic Protection command.
The fourth victim, also hit by the car, was Leslie Rhodes, 75, from Clapham in south-west London, who died in hospital, when his life support was switched off.
A dozen people received serious injuries, some described as "catastrophic", and eight others were treated for less serious injuries at the scene.
Injured members of the public were taken to St Thomas' Hospital, which is located immediately across Westminster Bridge in Lambeth, and to King's College Hospital (which declared a 'major incident' in its designated trauma centre), St Mary's Hospital, the Royal London Hospital and the Chelsea and Westminster Hospital.
Two Romanian citizens were injured, one of whom had to be rescued from the River Thames after being thrown from the bridge by the car of the attacker, and was injured severely.
Others included three police officers who were returning from a commendation ceremony, and four students from Edge Hill University in Lancashire.
Born Adrian Russell Elms, later changed to Adrian Russell Ajao, when he took the name of his step-father.
Masood was born in Kent, brought up initially in Rye, East Sussex and was most recently living in the West Midlands.
When he was 16 he dropped out of school and by 18 he was taking drugs and was described as a "heavy cocaine" user.
Masood was reported to have been a teacher of English in Saudi Arabia sometime between 2005 to 2009.
Local media report that in 2009 he underwent conversion to Islam while in prison, after which he changed his name to Khalid Masood, though police have said he also used several other aliases, including Khalid Choudry.
Although he had been previously investigated by MI5, Scotland Yard said that Masood was not the subject of any current investigations and there was no prior intelligence about his intent to mount a terrorist attack.
He had a range of previous convictions for assaults, including grievous bodily harm, possession of offensive weapons and public order offences going back to 1983.
Masood spent the night before the attack at the Preston Park Hotel in Brighton in Sussex and was described as "laughing and joking" by the manager there.
The motivation for the attack is suspected by authorities to be Islamic extremism, although Home Secretary Amber Rudd cast doubt over whether Masood was formally affiliated with ISIL.
On 23 March, ISIL's unofficial news channel, Amaq News Agency announced that the attacker was "a soldier of the Islamic State, executing the operation in response to calls to target citizens of coalition nations".
Analysts monitoring the group online said the claim appears to be an effort to disguise ISIL's losses in Iraq and Syria, adding that the lack of biographical information of the attacker and lack of specifics about the attack suggested it was not directly involved.
Some early reports gave descriptions of two supposed attackers, one described as a "bald white man" and another as a "black man with goatee beard"; however, Mark Rowley, the Metropolitan Police's Assistant Commissioner for Specialist Operations, dismissed these claims, saying that the attack was a lone wolf attack.
Abu Izzadeen was also erroneously identified as the attacker on social media, Channel 4 News and The Independent shortly after the attack, Izzadeen however was actually in prison at the time.
By the morning of 23 March, six addresses had been raided in East London and Birmingham resulting in the arrests of eight people for suspicion of preparing terrorist acts.
By 24 March three further arrests had been made in the West Midlands, the North West of England and in Manchester.
Later on 24 March seven of those initially arrested were released without further action and one woman from Manchester was released on bail, leaving two men from Birmingham still in custody.
The various reactions to the terrorist attack in England, both domestic and international, expressed shock and outrage, and it has been considered as an attack against liberty, freedom of speech, and democracy.
Those evil and twisted individuals who try to destroy our shared way of life will never succeed and we condemn them.
On behalf of members of both Houses of Parliament, we wish to offer our thoughts to all those affected and their families.
The Scottish Parliament suspended the day's proceedings, including a debate on a second independence referendum.
Some MSPs who opponed the decision to suspend parliament said that doing so was "giving in to terrorism".
Both the House of Commons and the House of Lords resumed their normal functions on 23 March, the day after the attack.
A one-minute silence in honour of the dead was observed in Parliament, and by London's emergency services, at 9.33 am.
Yesterday an act of terrorism tried to silence our democracy, but today we meet as normal, as generations have done before us and as future generations will continue to do, to deliver a simple message: We are not afraid and our resolve will never waver in the face of terrorism.
The Labour leader Jeremy Corbyn, the Leader of the Opposition, described the attack as "an appalling atrocity".
In honour of PC Palmer, his police uniform and shoulder number 4157U were permanently retired; Charlton Athletic F.C.
announced that his season ticket seat at The Valley would not be occupied at the club's next home game, but would instead have a club scarf placed over it as a mark of respect.
A JustGiving fund was set up, with the target of raising £100,000 for his family, a goal attained in less than 24 hours. A group called "Muslims United for London" also raised over £16,000 to support victims and victims' families, releasing a statement saying, "The British Muslim community stands with the community during these difficult times."
Also on 24 March, Tobias Elwood was appointed to the Privy Council for his role in rendering aid to PC Palmer, as was security minister Ben Wallace MP, who helped coordinate the government response.
In addition to the expressions of shock, support, solidarity and sympathy offered by several national governments,[a] the United Nations Security Council observed a minute of silence at its morning meeting on 23 March.
The attack was denounced by the European Commission President Jean-Claude Juncker and the Organisation of Islamic Cooperation.
Followers of ISIL channels on social media celebrated the attack as revenge for British airstrikes against the group in Syria and Iraq.
Amaq News Agency later claimed the attacker had responded to ISIL's call to attack coalition citizens.
On the evening of the attack, the Brandenburg Gate in Germany and Tel Aviv City Hall in Israel were illuminated with the Union Jack.
At midnight that day the Eiffel Tower's lights were switched off to honour those killed in the London attack.