THE police officer killed in the terror melee was Constable Keith Palmer, a 15-year veteran of the force and a father of two.
The 48-year-old was a member of the parliamentary and diplomatic protection command that usually are armed and stand guard just within the gates of the Houses of Parliament.
There are reports he was not armed at the time the lone wolf attacker lunged at him with two knives; instantly several of his colleagues rushed to his aid but he died of his wounds.
London Mayor Sadiq Khan described the actions of PC Palmer as "courageous".
"Keith Palmer was killed while bravely doing his duty - protecting our city and the heart of our democracy from those who want to destroy our way of life," he said.
"My heart goes out to his family, friends and colleagues. He personifies the brave men and women of our police and emergency services who work around the clock to keep us safe - tonight all Londoners are grateful to them."
Tory MP James Cleverly described his close friend as "a brave man".
"I've known Keith for 25 years. We served together in the Royal Artillery before he became a copper. A lovely man, a friend. Im heartbroken," he tweeted.