The incident took place shortly after 8.30pm on Friday when a suspect deliberately drove a car at police outside the palace then reached for a 4ft sword.

The unarmed officers were injured after they tackled the driver, with two suffering minor cuts.

The Metropolitan Police said it had arrested a 30-year-old on suspicion of grievous bodily harm and assault on police and that he was later additionally placed under arrest under the Terrorism Act 2000.

Police have been given permission to hold the man until September 1.

A 26-year-old man from Luton who was arrested at the scene remains in custody. Police said CS gas was used as part of the arrest and during the struggle he repeatedly shouted the words "Allahu Akbar."