The Forth Railway Bridge stretches almost 2.5km across the Firth of Forth, a large estuary area to west of Edinburgh. The bridge, which features two main spans of over 500m each, continues to operate as vital rail link between Fife and the Lothians.

The Forth Bridge was designed by the English engineers Sir John Fowler and Sir Benjamin Baker using the cantilever principle in which a central span is supported by the tension and compression of supporting arms that are only anchored at one end.

Before construction even began on the bridge in 1882, the contractor Sir William Arrol & Co. ...