What is the most exclusive tartan?
That’s difficult. One answer could be that a personal tartan made for one man would be the most exclusive. Perhaps you mean which is the most desirable tartan and the answer to that could be the Balmoral tartan which was designed by Queen Victoria’s husband, Prince Albert and which can only be worn by the Royal Family. No weaver in the United Kingdom would produce that for anyone other than the Royal Family. Some overseas weavers have ignored the longstanding convention and produced what purports to be Balmoral. Such behaviour is viewed with great disdain by the Scottish industry and anyone who wore it in Scotland would be committing a great social (but not legal) sin!