Thanks for this definitive answer, 34 and Johnster. Baccy 57XX it will be. I'm modelling Dee Valley around Corwen, specifically 1938-9, but since Corwen was such a horribly elongated site, I have predicated another GWR/LMS junction nearby, on the lines of the LNWR Betws-y-Coed - Corwen proposal never taken forward, and created it a bit wider and stumpier than even a compressed Corwen would have been.