Nobody watching " The Steeltown Murders"? This drama, based on a true story is set in South Wales in two timelines, the first being 1973 the second in the early 2000s . In the 1973 era, a MGR hauled by a large logo livery class 56 appears in the background twice, the first time the logo is the wrong way round, the second time the train is going the opposite direction and the logo is right way round. The loco also has small white numbers. Can't help thinking it might have been CGI but at usual plenty of attention had been made to ensure the correct cars and vans are used, but when a train is needed, anything will do.
Jim