Peter Kerslake says "An interesting photograph of a Western Region locomotive with a Western Region footplatemen displaying Western Region lamps arranged in a Southern Region route indicating manner and heading a train of Southern Region stock.
The explanation is that this is one of such workings over the Southern "Withered Arm" line from Plymouth to Exeter running via Okehampton and North Dartmoor in order to familiarise Western crews with that line in the event of a blockage of the Western Region main line between Exeter and Plymouth, often due to storm conditions at Dawlish, with similar exchange daily workings by Southern Region Bulleid "Pacifics" and Southern crews on the Western main line.
The working seen here would have started from Plymouth's Southern Region Friary station and although bound for Exeter is facing west ready to take the Southern line.
"Moguls" were the largest Western Region locomotives permitted to work the Southern line, and on 22nd. November, 1953 following a freight derailment on Dainton bank the down "Cornish Riviera" reached Plymouth several hours late via the Southern line double headed by 6379 and 5360".

Martin Tester says "I would say this is 1956 - certainly no earlier. 6385 was painted fully lined green with a small version of the first BR emblem for Royal Train duties in May 1956 (double heading Taunton to Barnstaple with similarly finished 6372). Here 6385 looks to be in that condition. Also in Maidment's book on the Moguls (p147) there is a photo of 6385 at Exeter St Davids having arrived from Plymouth via Okehampton. The date is given as May 1956. Interestingly the SR stock (3-car set 447) is in BR carmine & cream."