POLICE are calling for witnesses after a man was left in a critical condition and two other people seriously injured in a head on collision on the A414 this morning (Friday).

The accident happened at around 7.40am, when a silver Peugeot 106 heading towards Hatfield crossed the central reservation and collided head on with a Mercedes travelling in the opposite direction.

The Mercedes driver, a 38 year old man from London Colney, suffered serious head injuries and was taken to the London Royal Free Hospital by air ambulance. His condition is believed to be critical.

The driver of the Peugeot, a 22-year-old man from Bayford, and his passenger, a 20-year-old girl from Hertford, suffered serious back injuries and were taken to the QE2 Hospital in WGC.

The road was closed between for five hours between Cole Green and Hertingfordbury as police, firefighters, paramedics and the Herts Air Ambulance all attended the scene.

Anyone who saw the accident or has any information should call Hertfordshire Constabulary on 0845 3300 222.