In 1923 the 120 Railways of Britain were combined into the ‘Big Four’ Consisting of the London, North Eastern Railway, the London, Midland and Scotland railway, the Great Western Railway and the Southern Railway. After WW2 in 1948 the Big Four were united into British Railways. During The 1950’s-60’s steam was withdrawn and replaced by Diesel and Electric engines.

Here we see a diagram of a American Electric Locomotive. Diesel Engines work almost Identically (they just burn oil)