These are the latest two locos from the Hornby TT 120 stable and are little beauties.
Montrose has the old crest so pulling some early livery Staniers, Abercorn has the later crest so in charge of the Mk1's
I will have to check Montrose's front driving wheels as twice she slipped the same point. I would take a guess it is her wheel as I have not had any other locos behave that way.