British police say the Westminster terror attack was over in less 90 seconds.

They say Khalid Masood acted alone in planning the attack.

He drove into pedestrians on Westminster bridge in London, crashed his car, then fatally stabbed an officer guarding Parliament.

The family of PC Keith Palmer has thanked those who came to his aid, saying there was nothing more they could have done.

Policing analyst says officers did the best they could: