A man has been detained by armed police outside the Palace of Westminster.
A bearded man, wearing black trousers and a grey sweatshirt, was seen being held against the fence with his arms behind his back by a police officer.
The incident is not thought to be terror related. The Carriage Gates entrance to Parliament is closed.
Evening Standard political editor Joe Murphy tweeted that there were shouts of “knife, knife, knife” and a man was brought down with a Taser.
Scotland Yard said the man – aged in his 30s – was arrested on suspicion of possessing a knife.
There are no reported injuries.