Passengers were left delayed and confused when a rail crew got their lines crossed and took the wrong train out of a station.
The driver and train manager went to Banbury in Oxfordshire where they were due to take control of the service to London Paddington.
But instead they got on the train heading to Swansea and set off toward South Wales.
The First Great Western crew realised their mistake a short distance down the line and decided to head back to Banbury to get the right train.
Other trains were held up to clear the way for their return back up the same line to Banbury.
There the crew got on the right train to London which set off over half an hour late on Monday night.
First Great Western confirmed the crew boarded the Paddington to Swansea train at Banbury, but should have got on the Swansea to Paddington service.