Yes, it was length of traverser and the size of the shops - 39’: Glover tanks needed their buffers removed to fit in! Whether the GN actually needed a 4-6-0 is also a moot point….the proposal came along in 1911, before Glover’s arrival and the design of the S class. As an NER man, Glover was well used to 4-6-0s but obviously chose not to build his own. Indeed, on the NE Glover would have seen how Worsdell’s R class 4-4-0s took over work that the 4-6-0s struggled with! Pic by M Peirson.
The S proved that a large 4-4-0 could effectively do anything the GN asked of it and an S on form with a top crew was even a match for the V and VS. And unlike them, it could also work the Derry Road - and even reach Enniskillen if the civil engineer wasn’t looking…..
Sorry Patrick - thread creep!! What would Mr Weaver say?