Five people have died and at least 40 have been injured in the terror attack in London yesterday.
The rampage by a knifeman at Westminster began on Wednesday (March 22), when he mowed down pedestrians on Westminster Bridge before stabbing to death a policeman inside the gates of Parliament before being shot dead by other officers.
The dead officer has now been named as PC Keith Palmer, 48, a husband and father.
PM Theresa May said the attack was "sick and depraved" and struck at values of liberty, democracy and freedom of speech.
The attacker has not been named by police.
Pocklington MP Sir Greg Knight was at Westminster when the attack began.
Following the incident he tweeted: "Parliament lockdown now over. My thoughts are with the innocent victims.
He later posted: "Both the House of Commons and the House of Lords will sit tomorrow at their normal times."
A minute of silence will be held at Parliament at 9.30am this morning.