MPs have been leaving tributes to PC Keith Palmer, who was killed in Wednesday's attack
The Houses of Parliament were on lockdown for hours as authorities dealt with the incident, which has left at least five people dead and around 40 injured.
MPs have praised the efforts of Met Police officer Keith Palmer, who confronted the attacker after he tried to storm Parliament but was tragically killed in the incident.
Mr Palmer, a 48-year-old husband and father, was fatally stabbed while stopping the killer.
Leading the tributes was James Cleverly, the Conservative MP for Braintree who served alongside Mr Palmer in the British Armed Forces.
Foreign Minister Boris Johnson's reaction to Wednesday's events
He tweeted: “Huge thank you to the security staff in Parliament, @metpoliceuk @LondonFire & @Ldn_Ambulance for their great work today.
“I’ve known Keith for 25 years. We served together in the Royal Artillery before he became a copper. A lovely man, a friend. I'm heartbroken.
Jeremy Corbyn's statement following the attack
Great Yarmouth MP Brandon Lewis tweeted his condolences
“My thoughts are with the family, friends and colleagues of PC Keith Palmer. A brave man.”
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Nigel Huddleston, the Tory MP for Mid Worcestershire, wrote: “I & all MPs will be forever grateful to PC Keith Palmer who gave his life to protect us today. Our thoughts and prayers are with his family.”
London Mayor Sadiq Khan tweeted a brief statement, in which he praised the “courageous police officer” and said the people of London “are grateful to him”.
Former Ukip leader Nigel Farage said he was 'not surprised' by the attack
Former PM David Cameron's tribute
The statement read: “Tonight we have learned that the courageous police officer who was killed while protecting our city was PC Keith Palmer. He was 48 and a husband and father.
“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.
“My heart goes out to his family, friends and colleagues.
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Conservative MP Tobias Ellwood (centre) helps emergency services attend to a police officer outside the Palace of Westminster, London
“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.”
Other notable political figures also offered tributes to the victims of Wednesday’s attack, thanking him for his service to his country.
Tory MP Helen Whately braded the attack 'disgusting'
Lib Dem leader Tim Farron applauded the police for their efforts
Former Labour leader Ed Miliband wrote: “We all mourn for PC Keith Palmer and send the deepest condolences to his family. He died protecting all of us at Westminster.”
Tory MP David Lidington, Lord President of the Council & Leader of House of Commons, added: “Entire House of Commons united in thanks to our police & security staff today and heartfelt sympathy for those who were injured or bereaved.”