SR N15 4-6-0 No 767 Sir Valence with a down express waiting to leave Cannon Street in c1932. The year 1925 as originally thought is a bit too early - the 'high-windowed' coach to the right was later than that 1929, plus it does not look brand new.
Peter Swift adds some more detail " 767 received a 400 gallon 6-wneel tender in Feb 1930 and lost its E-prefix in 9/1931 so has to be later than that date. And yes the high-window stock started to appear in 1928.
Interestingly it was allocated to Stewarts Lane shed and was used on Central Division services to Brighton and Eastbourne. Can’t be sure but suspect the photo date is post-electrification of the Brighton main line in 1932."