i am a frequent user of Euston and on the infrequent time a train platform is announced late then I have rarely seen a manual ticket check before boarding.
There are surges when platforms are announced but I have never seen elderley or disabled people knocked over or even pushed aside.
Most trains are announced some 15-20mins before departure and if its a Virgin train final boarding is announced 5 minutes (not 3) before departure.
As another frequent user of Euston, usually at weekends, this is not a picture I recognise. Trains being announced at short notice is a frequent occurrence.
I've seen a man on crutches not make his train because by the time the melée had fought their way on -- the previous train having been cancelled -- there was no physical space. I've seen the same happen to elderly people. The people who check tickets there are generally an unpleasant bunch too in my experience.
You often get three or more Pendolinos' worth of passengers waiting in the main hall, and it can get quite squashed in there. When a late-running train then arrives and passengers hurry off, it can get positively dangerous.
I'm amazed Virgin have been allowed to run Euston this way for several years now.
The situation on Platform 7 at Liverpool Lime Street can get quite bad as well on the first train after a match. There's a complete lack of organisation there and the "queue", such as it is, can go as far back as far as the gents. They generally wait until about 8 minutes before the train is due to leave before letting people on to the platform proper, and then insist on doing a full ticket check with just two people, while another two look on idly.