David J. Hayes says " Again, although pre-dating the image, the May 1969-May 1970 WTT may provide a clue as to what this working might be. 8O63 back then was shown as the 22:00 SSuX Manned Conditional service from Willesden Sudbury Sidings to Norwood Yard (arr. 23:22). It was booked through Kensington Olympia at 22:20. Although that would have made it too dark for conventional photography (no digital cameras back then!), it may have been running to earlier timings as of June 1970 when it may have still been just possible to capture it on film as late in the evening as, say, 9pm.