The Black Watch Tartan was said to be used by the Independent Companies. They policed the Highlands under General Wade who were formed in 1725 and later evolved into the Black Watch in 1739. The tartan has been known by various names.
It was worn in the proscribed period (1746-1782), when highland dress was banned by an Act of Parliament by Government servants and regiments in American wars. Thus it was called the 'Government' or 'Hanoverian' tartan. It is the same tartan as the Campbell clan tartan. The reason is much argued. It might be that out of the original six Independent Companies four were commanded by Campbells. These days it is used as a 'Universal' tartan so wearable by anyone who has no tartan or clan connections.