Peter Kerslake says "This image of the down "Cheltenham Spa Express" about to leave Paddington shows it with not the usual single "Castle" at the head but on this day, for some reason, it is double headed by two of the class....super power for a super train indeed!
The pilot engine, 7035, "Ogmore Castle" is one of Gloucester 's own, which would be a customary sight on this departure, but the note to this picture indicates the train engine as being 7000, "Viscount Portal", a Newton Abbot engine, which is surprising, but perhaps it was an unbalanced duty which brought it into London and this is one way of working it back home to Newton Abbot via Gloucester.
The Reporting Number puzzles me as those beginning with "5" were for Paddington bound expresses working up from the Torquay line and down workings from Paddington began with a "1", so it's all a bit strang !
The plot thickens! The date 1955-05-03 is incorrect as both 7035 & 7000 were coupled to
Hawksworth tenders at that time.
The “CSE” carried reporting number 512 between 1958-09-11 and 1959-06-13 when both locos had Collett tenders, but 7035 was not allocated to 85B during this period".