Paul Warner says " The train appears to be starting away from the up loop at Langley Crossing. The bridge in the distance seems right for the location and if you look through a magnifying glas you can make out a signal in front of it. this would be Langley crossing's section signal with Chippenham East's distant underneath "
The guard is hanging off the steps of his brake van presumably to see his train away safety - lets hope there was not a jerk.