An Ivatt 2MT 2-6-2T I suspect. Llandudno Junction had an allocation and when they replaced the Ivatt/Stanier 3MT 2-6-2Ts they were popular as, despite being theoretically less powerful, they were more capable locos.Was that a 2-6-4T at BF? Would that be there on a pick-up goods?
And they became the regular choice for the branch freight.
Other delights I noticed on the film were the Crosville bus crew watching the proceedings, the condemned coach parked in the goods yard (why?) and the old lady wandering casually through the winching operation at 6.48 ! Health & Safety? Never heard of it.