Ultimately the train crew manage the train. If they refuse on the point of safety (overcrowding) then the train will be sitting at Bath and won't go anywhere until some sort of mutual agreement is sorted between Control and the crew. Seeing as the crew on the the train are critical to the movement, I know who will win...
That being said I've only once before seen that conflict being protracted - if crew were to "refuse" a call order, that's the end of the matter normally, but its incredibly rare (normally on some sort of safety reason, like here).
Also maybe there was a crew-change on route so one crew agrees it but the situation then changes? I don't think that happened here, but something to consider.
Indeed. Again speaking based on my experience, train crew basically want to get their jobs done with the minimum of hassle, and certainly aren’t going to quibble not to call orders unless there is a very good reason why (and dangerous overcrowding is certainly one such a reason). Another reason might be the signaller telling you the points have failed so you’re stuck on the through lines with no platform at the station you’re booked to call at…
This kind of thing works both ways. I had the TM call me a few weeks back and report that we had a group who had boarded the wrong train, wanting the next town along, when we were direct to London. It was agreed with control and with the signaller that we would stop additionally to let them off (additional calls, or agreements no to call can be agreed directly with the signaller in lieu of an order). It’s a question of balancing the slight delay to the service versus helping out those who have made an innocent error, plus the possible risk of someone over carried pulling a passcom which leads on to potential safety issues.