ODD: I looked on opentraintimes, was listed as a HST▸ .
That would be the timing. All high speed services are currently timed as HSTs.
There was a 9 coach HST going around at some point, though.
Adding to that picture ... many current timings for
Timed for 90mph max
Pathed as Class 158 (Express Sprinter) DMU▸
turn out to be class 165 or 166
and timings for
Timed for 75mph max
Pathed as Class 150/153/155/156 (Sprinter) DMU
Are oft run by 158, 165 or 166 units.
I can't recall when a 155 or 156 last appeared at Westbury - from which I have taken those latest quotes