A 75-year-old man seriously injured in the Westminster terror attack has died in hospital after his life support was turned off.
The man, who has not been named, died at King's College Hospital and his family have been informed.
It takes the number killed by Khalid Masood in Wednesday's atrocity in central London to four. He was also shot dead.
On Thursday evening Londoners came together in Trafalgar Square for a candlelit vigil to show defiance and solidarity.
London Mayor Sadiq Khan told the packed square: "Those evil and twisted individuals who tried to destroy our shared way of life will never succeed and we condemn them.
"When Londoners face adversity we always pull together. We stand up for our values and show the world we are the greatest city in the world."
A young woman told Sky News: "We all have to stick together and show support and solidarity. They might have scared us but they won't beat us."
A man who said he was from the Muslim community added: "This is our home. You've got to stand together.
"When you get such a person as this - I cannot even express what sort of brain he had. This is time to show we are together.
"Love for all; hatred for none - that is our message. The word Islam means peace. Going out and doing this sort of atrocity is... (the) opposite of Islam."
Teacher Aysha Frade and US tourist Kurt Cochran were the two other civilians killed when Masood drove his Hyundai into pedestrians on Westminster Bridge.
Unarmed policeman PC Keith Palmer, 48, was then stabbed to death by the 52-year-old terrorist in the grounds of Parliament.
Dozens of other people were injured, including nationals of Britain, France, Romania, South Korea, Greece, Germany, Poland, Ireland, China, Italy and the US.
Kent-born Masood, who was shot dead by police 20 metres inside the gates of Parliament, used a number of aliases and was investigated by MI5 some years ago over concerns of violent extremism.
Islamic State claimed the killer was one of its "soldiers", but Home Secretary Amber Rudd denied there had been an intelligence failure.
A review of security is taking place at Parliament.
:: Sky News will be showing a special programme - Terror In Westminster - at 7.30pm tonight