I presume you are referring to London Kings Cross to Bradford Exchange trains. In referring to 'Standard' 4MT tanks (in particular, starting 'Standard' with a capital letter), the implication seems to be that the type referred to was the BR-designed 80000-80154. Whether that was your intention or not, that was not the type used, it was, in the tank engine era, LMS-designed Stanier/Fairburn tanks.
Stanier/Fairburn tanks, in this case from Manningham shed, also used to haul 'The Devonian' between Leeds City and Bradford Forster Square, but in that case the entire train continued from Leeds to Bradford. Luckily the route is pretty flat! In an afternoon the tank used to run light engine from Manningham to Leeds City to take up the working, I imagine the routine in the morning would have been the reverse. Of course, there needed to be a change of loco at Leeds City since the train reversed there, thereby denying Bradfordians like myself the delights of a Holbeck or Bristol Barrow Road allocated Jubilee, most days.