A Government minister was among the first to rush to the aid of the police officer fatally injured in the attack.
Foreign Office minister Tobias Ellwood rushed to the the officer after he was apparently stabbed just at the gates to the Palace of Westminster.
The former Army captain with the Royal Green Jackets helped paramedics deliver first aid to the officer.
He was seen covered in blood after he tried to help staunch the man’s wounds.
The BBC later reported that the officer had died as a result of his injuries,
A source close to Mr Ellwood told The Telegraph: “[He] tried to give mouth to mouth and stem blood flow from multiple stab wounds to the officer until the chopper and medics arrived”.
Mr Ellwood has been Parliamentary Under-Secretary at the Foreign Office since July 2014, covering the Middle East and Africa brief. He has been an MP for Bournemouth East since 2005.