A police officer on a motorbike was struck by a car he tried to stop yesterday.

A speeding BMW was flagged down on the A13 near Aveley by the officer before he led the driver down a slip road at the Ferry Lane roundabout in Rainham.

The car then hit the motorbike, causing the policeman to crash to ground on the roundabout into the path of another vehicle which braked hard to avoid him.

The flagged BMW driver then drove off and crashed into a wall near the roundabout, before leaving the car and running away from the scene.

A Metropolitan Police dog unit and helicopter helped track down the man before he was arrested.

A knife was also recovered.

An 18-year-old man from Grays was arrested on suspicion of attempted GBH with intent, dangerous driving, theft of a vehicle and possessing an offensive weapon.

The officer was taken to a hospital where he was treated for minor injuries.

Police are appealing for witnesses or anyone with information about the collision or the BMW to come forward.

Call Essex Police on 101 or email collisionappeal@essex.police.uk