London Reading in 23 then Reading to Swindon in 23. This sounds like a new benchmark.
I will still maintain that you could close most of the HST to AC gap with a high performance DMU that isn't being deliberately throttled but this is still impressive.
Are there many non stop runs to Reading in 180s to compare to this?
The fastest class 180 timing in Railway Performance Society archive is 23 min 26 - but i haven't looked at the detail to understand how good or bad the run was. As a guide, a Class 180 can beat an HST to 10 miles by 3/4 of a minute, so not quite as fast as an 800 - but not too far behind. All things being equal you would expect a healthy class 180 running on all engines - and with a determined driver to achieve under 23 minutes in the right conditions.
Paddington to Reading in 23 isn't a new benchmark. Less than 22 minutes would be. The current timetable allows for a net running time of 24 mins - plus 1 min recovery time - which a healthy HST can achieve without trying as long as everything else is running to time and there are no network issues.
If an HST service is running to time - most drivers are running up to around 120mph and coasting for large distances to dissipate time. Hence many of our recent timings reflect this relaxed state of driving. I expected some extra recovery time in the timetable to reflect additional trackside works - but current schedules are way too easy for an HST.
Where linespeed is 125mph, an 800 will gain at least 1 minutes advantage over a 10 mile station start on electric mode. There is no evidence to suggest braking or dwell times have improved significantly yet - probably the most experienced HST drivers can more confidently bring these to a stand than an 800?
As for Reading to Swindon - 23mins 14 was the best HST modern run under 'todays' driving standards. An 800 should be able to topple that by at least 1 minute , less the 20 seconds time loss changeover from electric to diesel and then back to electric at Stevenson. So somewhere in the region of 22.5 mins would be the hoped for benchmark. Probably only achievable if the train is running significantly late to incentivise the driver to run 'flat out' .
Current running time is 26.5 minutes which includes 2 min recovery. So HST's are set a 24.5 minute running time - even though they can easily do it in 1 and a quarter minute less! This is why the current GWR timetable ranks pretty low in regards to average speeds compared to the other 125mph services!