Not having been present I know not what happened, but I have a suspicion that a member of the crew might have been assaulted, or felt in fear of assault, or felt that the train was overcrowded to a dangerous degree.
Members may recall an incident last Easter when the 18-03 terminated at Reading after an alleged assault.
Surely there is a
BTP▸ presence at Paddington, or were they on a donut break? If a member of staff "felt threatened", the culprit should have been removed by the BTP allowing the train to proceed?
As for overcrowding,
GWRs▸ default position is that it however bad it is, overcrowding doesn't represent a safety risk so can't imagine that would be the reason?
If memory serves the incident last Easter you referred to turned out to be a red herring?
Obviously I acknowledge that I/we are all speculating............although Broadgage's suggestions sound plausible........