I'm sure it's been discussed before either on this thread, or on the Imaginary Railways thread, but it's interesting to imagine what a UK railway system with a loading gauge more like that on the European mainland would have evolved in terms of motive power?
Even if we did have the larger loading gauge of our European friends, if we still retained the short goods loops and multiplicity of collieries, good yards etc., with sharp radius curves, and a large private owner wagon fleet wedded to the short wheelbase 4 wheel open or covered wagon with no continuous brakes, there's still little point in evolving impressive beasts like the French 4-8-2's, German Br01's, Br44's etc.