A POLICEMAN was knocked off his motorbike by a car he had tried to stop on the A13.

The officer had flagged down a BMW car, which was suspected of speeding, on the dual carriageway at 2pm today. 

He was leading the car up a slip road off the A13 at Ferry Lane, Rainham, when the car struck the rear of the motorbike. T

he officer was thrown to the ground on the Ferry Lane roundabout into the path of a vehicle which braked hard to avoid him.

The BMW drove away but struck a wall near the roundabout and the driver then ran off.

A Metropolitan Police dog unit and the police helicopter tracked the man and 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 treated at hospital for minor injuries.

Officers from the Essex Police Serious Collision Investigation Unit are investigating the incident and anyone who witnessed it or has information is asked to call 101 or email collisionappeal@essex.police.uk