The attack in Westminster appears to be a lone wolf, but this cannot be confirmed yet, a former Scotland Yard commander said.
Parliament is in lockdown after a man wielding a knife was shot outside, while a car mounted the pavement and hit several people on Westminster Bridge.
Former Scotland Yard commander John O'Connor told Jon Holmes: “It looks to me like it’s one of these lone wolf terrorist incidents, that can’t be confirmed yet.
“It’s the sort of thing I think Londoners and the police in London have grown to expect and learnt how to deal with," he added. “I’m very impressed with how quick the emergency services have responded.
“I think it’s virtually impossible to police against it, to anticipate it, all you can do is make sure you’ve got enough trained officers, you’ve got enough back up and enough contingency plans and that’s all you can do."
Listen to the full interview above