ITV News Political Correspondent Paul Brand is outside Parliament following reports a police officer has been stabbed and the assailant shot. He has tweeted:
Casualty still being seen to on Westminster bridge. Whole area now cordoned off.
All those arrested in connection with the Westminster attack have now been released by police.
Tony Davis was the first civilian to reach Pc Palmer after he was stabbed during the Westminster attack.
Defiant Londoners put on a show of solidarity for the victims of the Westminster terror attack at a vigil in their honour.