Passengers on a key commuter rail route were today expected to be given a 400m investment promise.

The pledge is likely from M40 Trains, which runs the London to Birmingham Chiltern Trains' service through Oxfordshire.

The cash boost was accompanying the expected news that M40 had won the battle to continue operating its Chiltern franchise.

Eighteen of the 25 train company franchises are currently being renewed and the Chiltern route, heavily used by commuters from Buckinghamshire and Oxfordshire, is the first to be re-franchised.

M40 Trains began running Chiltern in July 1996.