There was only a very modest increase in line speed with electrification in 1967 - from 40 to 45, IIRC. In practice, speed limits were largely academic until the arrival of the 1938 stock in 1989, because neither the O2 tanks nor the 'Standard' tube stock were fitted with speedometers. I remember one quite exhilarating - and slightly scary - occasion in 1988, when I was guard on the 'boat train' and the driver was 'caught short' during the turnround at Shanklin. We eventually departed six minutes late, much to the chagrin of passengers hoping to connect with the catamaran. It was clear from the outset that the driver was 'going for it' and once we left Sandown all hell let loose. Even though this (by then singled) section was laid with 60 foot flat-bottom rail, the vertical and lateral motion (of the passengers as well as the train) had to be seen to be believed! at the bottom of the bank on Moreton Common, I did a discreet quarter milepost timing and worked out that we had been doing 66 mph. We arrived at the Pierhead one minute down and the passengers made their connection, shaken but not stirred! I've never felt able to put this writing up to now, but the driver concerned is long since retired and probably no longer with us.....one of the great island railway characters!