I recall reading that sometime in the 1980s, Shrewsbury station staff placed a platform seat in a van of a parcels train, as a means of getting some stranded passengers home towards South Wales.
I also recall reading that one day in the 1970s, a Deltic on the up Yorkshire Pullman from Bradford Exchange failed approaching Leeds, blocking or locking up quite a lot of the west end of the station; and that the engine and train were rescued and dragged into the station by a two-car dmu, I think a Cravens one. The din and rattle must have been memorable!
On the WR, the South Wales Pullman failed once or twice, especially in the era when it was diagrammed for a Hymek, which was not really strong enough for the job. Pictures exist of its being run from Newport to Cardiff behind tank engines, at least once a 94xx.
I think the most amazing substitute traction story is related by Adrian Vaughan in one of his trilogy of "Signalman's" books, about the time when the down "Blue Pullman" failed somewhere between Didcot and Swindon, and was rescued by being coupled to a local stopping train hauled by a prairie tank. That train, of course, was vacuum braked only, and the Pullman set was air braked only, but they somehow managed to release its brakes and haul the whole of it very carefully as a "total swinger" behind the local. This probably broke many rules, but at least it got the Pullman passengers rescued as far as Swindon where they would have had to await onward services.
John Prytherch.