You can't stand in the way of progress and in 1922/23 the Metropolitan-Vickers electric loco was introduced.
Dad commuted into London in the late fifties to early sixties during the last days of steam and remembers these machines.
Trains from Aylesbury and points north would pause to uncouple the steam engine at Rickmansworth and continue, electric hauled, to Baker Street and beyond.
Out of the twenty built two remain. One is in the London Transport museum and another,
Sarah Siddons, is preserved in running order for special occasions, enthusiast trips, etc.
As a bonus, there's a steam loco on the other end.