The M40 has been shut southbound because of a "serious road traffic collision".

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The carriageway is closed between junction 4 for Handy Cross and junction 3 for Loudwater according to Highways England. 

Divers are advised to divert onto the A404 from junction four to High Wycombe and then to the A40 east to re-join the M40 at junction 3.

More as we get it.