I'm going to stick my neck out a bit with this slide. 31437 heads south at Clay Cross with a cross country service. I believe that this is probably 1O86 the 1400 Leeds to Brighton service.
31437 is recorded on the Chesterfield Observer as working 1E31 the 1413 Portsmouth to York service later the same day which puts it in the area. Can anyone confirm the train one way or the other.
Slide dated 19/4/86.
Photographer unknown.