I've heard it all now. HSTs are "slow accelerating old trains".
Oh the innocence of youth? However did we survive the ordeal of a Black 5 with 9 on leaving Wellingborough on the up? (I was too young to experience the pure torture of the compounds.)
How can you be disbelieving of comments from those that regularly travel on the MML when you openly admit in post #13
"But I do not use MML regularly -", you clearly have not had much experience of just how slow the HSTs do regain linespeed when checked or after a station stop.
It's one thing looking at maximum speeds and distances in the relatively quiet parts of the MML then making assumptions of how little time a journey could take. But the reality of overall MML service is as several here have said, i.e. For the first 50 miles out of St Pancras, the 5 MML timetabled trains per hour share track access with 4 trains to Bedford, 2 trains to Luton, 2 trains to St Albans and 2 to West Hampstead Thameslink, which is the 13:00 - 14:00 off peak passenger timetable. Then add the potential congestion caused by the terminators, MML ECS movements at St Pancras and Thameslink at Bedford, plus somewhere in there there are typically 3-4 freight paths which may be taken up.
With all that, mostly the timetables are kept to within 3-5 minutes. The EMUs just nip in and out of the fast lines in their slots. When a MML service is delayed in its path, the speed drops and (particularly the HSTs) struggle to get back up to speed, which means that they are then the obstruction for the EMUs. Somehwere, I've seen a you tube video taken from a 319 whis departed at the same time as an HST. The 319 (on the slow line) was travelling at around 50mph before the HST started to catch up, (just in time to slow down for the next signal check).