I also heard, while photographing today's HST, that 1W02 London Paddington to Hereford on 04/05/19 will be a HST, though I'm taking that with a pinch of salt as it seems unlikely to me that an individual diagram would be planned that far ahead?
On the contrary, it is likely that all of the remaining HST workings on the GWR are already planned (subject to rare contingency out and back workings which can be substituted on an as required basis). HST workings need to start from and end at one of Laira, Long Rock and St Philips Marsh and be worked by staff who still sign the traction.
Just using RTT, it doesn't look very likely that 1W02 London Paddington to Hereford on 04/05/19 will be a HST because to be one, you would need there to be workings from one of the three places noted above which fit with its times at Paddington.
However, with engineering work meaning that West of England trains are heavily altered, with longer journey times for the route via Melksham meaning shorter time at Paddington, if the journey time to and from Hereford fits best with workings from Plymouth I guess it is possible with workings swapped.
By 4 May, according to diagrams on the 125 group website, there are only three weekday workings for 2+8 HSTs, two finishing at Laira on a Friday night and one at Penzance so all of the HST workings on 4 May must be out and back from those locations.
So,
if you are right, the working on 4 May would need to be:
5A75 03+15 Laira T.& R.S.M.D. to Plymouth 0337
1A75 0540 Plymouth to London Paddington 0936
1W02 1022 London Paddington to Hereford 1340
5W02 13+45 Hereford to Hereford 1401
5P65 14+58 Hereford to Hereford 1511
1P65 1513 Hereford to London Paddington 1829
1C96 2000 London Paddington to Plymouth 2345 (or maybe on 1C95 at 1848)
5C96 23+57 Plymouth to Laira T.& R.S.M.D. 0135
with the other two doing Plymouth-Paddington-Penzance and Penzance-Paddington-Plymouth. An eight hour round trip to Hereford is possibly the easiest place to send the High Speed Train given the changes to timetables.
On a normal Saturday, it is 1A76 0657 PLY-PAD 1010, 1C79 1103 PAD-PLY 1431, 1A89 1501 PLY-PAD 1821, 1C95 1903 PAD-PLY 2238 but 1Z76 arrives at Paddington at 1042, 1C79 leaves at 1048, 1Z89 arrives at Paddington at 1843, 1C95 leaves at 1848.
I guess we will wait and see.
