Thanks, yes the Wimbledon to Sutton link, opened by the Southern in 1930 was a line definitely built for electric traction due to the gradients and curves (having said that they used a steam loco to iron out the tracks and ballast when it was first built). The gradient and curves on the section from Sutton to West Sutton that you can see drop away in the picture used to be bordered by fresh white high concrete walls (now weathered and faded) and railwaymen nicknamed it "The Wall of Death" after the fairground ride of the same name.