The Forth, if you didn’t already know, is an expansive estuary that bisects the south-east of Scotland from the North Sea to 55 miles inland, with its vast mouth between Edinburgh and Fife linked by the three monumental engineering feats of the Forth Bridges. The estuary feeds into the very heart of Scotland so capturing it would have allowed invading armies easy access to Scotland’s biggest cities – which is one of the reasons why the powerful Crichton family decided to build such a heavily defended fortress between the Royal palaces at Linlithgow and Edinburgh over 600 years ago. It certainly would have been almost impossible to siege the place back in the 1400s, and the massive size of Blackness’s fortifications are still impressive to this day.