People walk around Westminster in London, Britain, on Aug. 15, 2018, a day after a man was arrested on suspicion of terror offences after a car crashed into security barriers outside the Houses of Parliament. (Xinhua/Ray Tang)

Cyclists ride over Westminster Bridge in London, Britain, on Aug. 15, 2018, a day after a man was arrested on suspicion of terror offences after a car crashed into security barriers outside the Houses of Parliament. (Xinhua/Ray Tang)

Policemen guard a gate outside the Houses of Parliament in London, Britain, on Aug. 15, 2018, a day after a man was arrested on suspicion of terror offences after a car crashed into security barriers outside the Houses of Parliament. (Xinhua/Ray Tang)

People walk past the Houses of Parliament in London, Britain, on Aug. 15, 2018, a day after a man was arrested on suspicion of terror offences after a car crashed into security barriers outside the Houses of Parliament. (Xinhua/Ray Tang)

Armed policemen stand guard outside the Houses of Parliament in London, Britain, on Aug. 15, 2018, a day after a man was arrested on suspicion of terror offences after a car crashed into security barriers outside the Houses of Parliament. (Xinhua/Ray Tang)