On Loch Fyne, Cowal Peninsula, Argyll.
Clan Lachlan (pronounced Lochlan) sent troops to fight for Prince Charles at the battle of Prestonpans (21 Sep 1745, east of Edinburgh) against the Hanoverian army led by Johnny Cope, whom they defeated. This was no mean feat since Argyll is Campbell country and they were not supporters of The Prince. Needless to say, the Hanoverians sent the navy to bombard the castle in 1746.
Old Castle Lachlan was built in roughly 1450 and is a category A listed building (HB no. 18294) and a scheduled monument (index no. 292).