On Sunday, I arrived at Euston on what should have been the 1110 arrival from Manchester. It arrived on P13 at 1055. As I reached the top of the ramp, the (delayed) 1049 Glasgow via WM was announced for P16. Cue the surge of passengers, who have no idea how long they now have before the train departs - it's already late remember, running for the train and almost taking me back down to the platforms with them (slight exaggeration, but you get the point). By the time I'd reached the toilets at the opposite end of the concourse, the same train was being announced with the added "please board the train now as it is ready to leave", which is a totally useless and unhelpful announcement which does nothing other than encourage further running and scrum like behaviour.
That's interesting - I caught the 10:49 Glasgow via BHM from Euston on Sunday. The incoming train was late, but roughly as it arrived in p16, RTT changed its platform status to confirmed so I joined a queue of about 20 - 30 people at the top of the ramp, before it went up on the screens.
On this occasion, as soon as the incoming pax had cleared the ramp, we were allowed down with no hold-ups, so I was ahead of any crowding. The set was in reverse formation, so I walked up to coach U as I didn't have a reservation, and when the train left at 11:09 that coach was still fairly empty. It didn't really fill up until Coventry.
We were scheduled to run slow line then Northampton loop, but in the event the track works must have completed early, I think we went to fast line at Ledburn and we certainly went main line via Kilsby not Northampton. As a result, despite the 20 minute late departure we reached Rugby early (and ahead of the 10:46 EUS to Glasgow via Trent Valley which had left on time but had run via Northampton - it passed us as we waited time at Rugby).