What remains of the horse-drawn Surrey Iron Railway that passed through Mitcham?
The Wandle Industrial Museum have a couple of rails and sleeper stones. The largest collection of sleeper stones was used by Youngs Brewery in Wandsworth, as part of a wall. The brewery closed and the site sold off in 2006. The stones remain in possession of the property developer.
The museum’s video gives the history of the railway:
My video includes photos of the pile of stones at the former brewery site. Their fate is unknown.
Wikipedia entry on the Surrey Iron Railway