The photograph was taken as the 05:53 BST train from Plymouth to London Paddington came out of a tunnel at Coryton, near Dawlish. This was at approx 06.40.
A spokesperson from FGW said: "First hand this photograph is frankly astonishing and appears to show behaviour that falls way short of the professional standards we expected from our train drivers."
"We have suspended a driver in relation to this incident, pending the outcome of a full investigation. He has not driven a train since we were made aware of this photograph," they added.