Tube-gauge steam locomotives may appear to be an unlikely possibility, because of the problems of using such a machine in the confines of a tunnel less than Category:Aldwych Branch The Short Streach Of Line Between Holborn And Aldwych Was Closed In 1994.The Line Was Due To be extended to Waterloo but never was.There will be a bit of Aldwych In My Website when added in diameter, but the London Underground had three such vehicles over the years. Two were built by the Hunslet Engine Company in 1899, and the third by Kerr, Stuart and Company in 1922.