Thank you for linking and posting that. It's raised a query though as it seems that the first six WR sets (253022-253027) transferred to the ER for MML services in 1982 before the final three sets had been formed. The final three (of eighteen) NE-SW sets would have been 253056-253058 but there is no mention of this and just a statement that they entered service as 254044-254046, with three TS vehicles (42114/42142/42158) converted to TFs (41175-41177), which would give an initial nine 2+7 sets for MML services.
So, did 253056-253058 ever operate as intended or did they actually enter service as 254044-254046? If the latter I wonder if this could be a possible explanation for the "missing" Lot No. of 30965 - if it was known that three TS vehicles were to be converted to TFs (41175-41177) someone initially planned to allocate the conversion a Lot No. in a similar way to the five prototype vehicles being converted to TFs (41170-41174) under Lot No. 30967 but it ultimately never happened. Pure speculation on my part I know!
I am 99% confident that the three sets concerned never ran in 'NESW' formation - happy to be proved wrong though! One thing I also think, but am not quite as confident about, is that 253053-055 initially ran with 41172-41174 in their formations, with 41167-41169 replacing them soon after.
I'm not sure the 'conversions' of the three TSs to 41175-41177 even involved a works visit - they may have been done at Neville Hill? (If so, perhaps that is why a Lot Number was de-issued, it was realised they didn't need works attention?).
I also wonder if the ER set released for MML duties was 254013? This would explain the availability of TRUK 40513 for conversion to the Executive Saloon given that initially all the MML sets operated in 2+7 formation (so technically 253s!). I assume the TRSB, 40030, would have been swapped with a TRUB from the WR.
253 053-55 ran with 41172-74 initially.
253 053 and 253 055 with 41172 and 41174 on 05.08.82, 253 054 noted with 41173, 09.10.82 and still in set 22.12.82.
253 053 had 41167 by 13.11.82, 253 054 had 41168 by 09.01.83, 253 055 had 41169 by 02.01.83.
In regard to the last 3 NE/SW formations, 253 056 certainly did operate for a short period, noted 23.08.82 on 10.20 Penzance-Newcastle and on 06.09.82 with 08.10 Newcastle-Plymouth. Formation on both dates 43177/120, 41167, 40035, 42322, 42126, 42122, 42134, 44000, 43120. I don't think 253 057/058 were ever formed up on the WR.
253 027 moved to the ER in October 81. When the MML HST service started there were initially only 5 diagrams NL 315-319. There were also 7 ECML diagrams for 2+7 TRUB sets, BN 301/2/3, NL 312/13 and HT 321/22. The ex-WR sets 253 022-026 (2+7) sets were absorbed in to the ECML fleet alongside 254 012-20 which were also 2+7 TRUB sets having lost their TRUK and TRSBs in exchange for ex-WR TRUBs in late 1981/early 1982. This pool of 15 sets covered the 12 ECML/MML 2+7 diagrams with none being dedicated to a particular route.
253 019-021 moved to the ER in May 1983, which in theory along with ex-253 022-027, 254 012-20 and 254 044/5/6 gave the ER a pool of 21 sets formed as 2+7. The number of ER 2+7 diagrams remained the same (seven) from 16.05.83, but the MML diagrams increased to 10 - NL 321-330.
In regard to the 3 ex NE-SW sets that became 254 044-046, I have no direct observation of the first (254 044) and can't find any elsewhere. Was it ever formed up?
254 045 was noted on 24.01.83 - 43062/93, 41174/3, 40349, 42138/130/134, 44093.
254 046 was noted on 31.05.83 - 43104/066, 41175/76, 40350, 42146/150/154, 44094 (40350 was noted on the WR 03.83).