Britain stood still today to pay tribute to the victims of the Westminster attack, from MPs and the police to Londoners in Trafalgar Square.
One day on from the events of Wednesday afternoon, the attacker has been named as 52-year-old Kent-born Khalid Masood and three victims have been named.
PM Theresa May addressed the Commons with defiance and mayor Sadiq Khan declared "we will not be cowed by terrorism".
Video report by ITV News correspondent Paul Davies.
Terrorists who carry out attacks like the one in Westminster "will not defeat us" and "will not win", Home Secretary Amber Rudd has declared.
Speaking at a candlelit vigil for victims of Wednesday's terror attack in central London Ms Rudd was defiant in her message to the gathered crowd, saying: "The terrorists will not defeat us, we will defeat them."
No police officers are under investigation following the Westminster terror attack, the Independent Police Complaints Commission has confirmed.
The IPCC is, however, "currently investigating the circumstances" in an independent investigation.
Deputy chair Sarah Green said: "The terrorist attack in Westminster on Wednesday was horrific and our thoughts are with all of those affected by it."
"It is important to stress that we are currently investigating the circumstances of the incident and no police officers are under investigation."
She added: "We are giving this investigation the highest priority and we will conclude it as soon as possible."
The Met Police's Acting Commissioner Craig Mackey has told Londoners that while Wednesday's tragic terror attack on Westminster "cannot be done" it is now up to the public to "choose our reaction".
Speaking at a candlelit vigil for victims of the attack he urged that Londoners "must stand together" as they "move forward" from what happened.
Scotland Yard has confirmed that eight people, three women and five men, have been arrested in London and Birmingham on suspicion of preparation of terrorist acts by detectives investigating the Westminster attack.
On Wednesday night, a 39-year-old woman was arrested in east London and a 21-year-old woman and a 23-year-old man were arrested at an address in Birmingham.
At a separate address in Birmingham a 26-year-old woman and three men aged 26, 27 and 28-years-old were also arrested.
On Thursday morning, an eighth arrest was made of a 58-year-old man at another address in Birmingham.
The force added that officers are continuing to search a number of addresses linked to the investigation - one in Carmarthenshire, west Wales, three in Birmingham and one in east London.
Crowds of people have begun to gather in Trafalgar Square for a candlelit vigil in honour of the victims of the Westminster terror attack.
Many arrived for the vigil carrying banners with messages including 'love for all, hatred for none' and bearing floral tributes for those who died on Wednesday.
Home Secretary Amber Rudd has said that the attack in London did not mean intelligence services had failed, saying it was "far too early" to understand the full picture of what happened and why.
Speaking to Julie Etchingham for a special edition of ITV's Tonight programme, Ms Rudd said: "This hasn't come as a complete surprise. We've been getting ready for this for a number of years."
She said that the attacker, Khalid Masood, was involved in a "historic" case, and therefore was not actively monitored.
"Intelligence services are working hard to put together the whole picture, but I would caution drawing conclusions yet," she added. "I would wait and see what comes forward from the intelligence that's going on now."
The Home Secretary refused to be drawn on what further information intelligence services had about the attacker, saying they were still investigating whether he was part of a network.
- You can see more of this interview on 'Terror in London: A Tonight Special' at 7.30pm on ITV