6109 1929c Bushey
LMS Royal Scot 4-6-0 No 6109 Royal Engineer with the 10am down 'Royal Scot' taking water from Bushey trough, there are several LMS period II coaches in the train which didn't enter traffic until 1930. Also in April 1931 smoke deflectors were added to 6109 so photo almost certainly taken in Summer 1930.
Photo: F.R. Hebron / Rail Archive Stephenson