The M40 has now been re-opened, but there is still  queueing traffic northbound between J2, A355 (Beaconsfield) and J3, A40 (Loudwater).

Thames Valley Police confirmed three cars were involved in the crash at around 6.30am this morning. Officers have said it has been deemed 'serious' with funeral directors spotted at the scene.

Congestion is now backing up to J1a - the junction with the M25.

More as we get it