English: Broad Gauge Railway Line (detail) During the 1890s the Great Western Railway was forced by Act of Parliament to change from their original 7ft 1in gauge to standard gauge, as a result they were left with miles of useless railway line. Much of it eventually went for scrap but some was recycled as structural reinforcement and as various types of fence post, as here.

This gives us an opportunity so see the cross-section of broad gauge railway line as it was used in the 19th century. Cast iron is an excellent material for use outside as it is not eaten away by rust when unprotected. When open to the elements it forms a thin patina of rust which protects the metal from further rusting.

It does, however, have one big disadvantage. Although very strong, especially in compression, it is brittle and will snap without warning before it bends.