As a matter of (my own) interest what, specifically, was the source of the stated 13:44 departure time?
Grahame's eyes I believe
My eyes, and Lee's eyes. We were watching the clock in my car (sorry, I drive occasionally). As we turned into the top of the slope down to the station, we saw the train already in significant motion - clock said 13:44. So surprised that we checked my car's clock against most of our mobile phones. Final check - Real Time Trains doesn't give Melksham departure times, but data on there was consistent with such an early departure.