Received its BR number in October 1949 after it was re-allocated away from Tunbridge Wells West shed. On Duty 668

From 'Southern Region Engine Workings', OPC, 1994: In 1960, Duty 668 was a Tunbridge Wells West working, allocated to '1P H Class P&P fitted' and went to Forest Row, then back and forth between Three Bridges and E Grinstead most of the morning, follwed by several hours on shed at Three Bridges, a bit more East Grinstead-Three Bridges, more shed time at TWW and finishing up with an evening working to Oxted before retiring for the night at TTW shed.
I have read that it was not entirely unknown for engine discs to be used without removing the pasted-on numerals applied for the the previous working (or two) so it is not guaranteed that the duty number applies to the working in the photo!