A naked man on the train tracks is believed to have been responsible for rail delays on Tuesday evening.
Passengers travelling on a Virgin Trains service heading north from London Euston said a naked man on the line close to Milton Keynes and Bletchley was responsible for causing the delays.
A British Transport Police spokesman said: “We received a report at 4.45pm on Tuesday of a man trespassing on the tracks in the Bletchley area.
“The incident was reported by a member of Network Rail staff.
“Trains were cautioned through the area at low speed while officers searched the location but there was no trace of the man.
“Normal running was resumed at 5.02pm.”
Virgin Trains was not available for comment.
Anyone with information is asked to contact British Transport Police on Freefone 0800 40 50 40, or text 61016, quoting incident reference 318 of 12/08/14.