The top boss of Chiltern Railways has stepped down.

Managing director Cath Proctor has been in charge since February 2004 and was seen as being responsible for putting the company back on track after the collapse of a tunnel at Gerrards Cross, Buckinghamshire, in 2005.

That incident lost the company a year's worth of growth, but it is now financially stable once more with passenger satisfaction at a six-year high.

Ms Proctor said: "I feel enormously proud of all that we have achieved and the way we have recovered ourselves after some very difficult times."

Adrian Shooter becomes acting managing director.

Ms Proctor will continue at the company as general manager and deputy to Mr Shooter until August 31.