The launch of http://www.new-north-press.co.uk/ website has the link to the excellent 'Reverting to Type' exhibition at The Standpoint  Gallery, of which I was part of the 'Portfolio of Artists' back in 2010 :

The small gauge rails used in my 11/11/11 Sculpture known as 2ft gauge, came from the surplus of the 1^st World War. They would have been used for the likes of tunnelling and to link up the main railheads at the rear with the front lines. After the war they were used to build railways like the Romney Hythe & Dymchurch line until worn beyond safety limits, when they are then scrapped.