Having reviewed plaid accessories and plaid dinner jackets I would be remiss if I did not mention the final and rarest plaid alternative: trousers. Or, more specifically, trews which are close-fitting tartan trousers that form part of Scottish Lowland Dress along with a Prince Charlie jacket or a dinner jacket.
Sartorially adventurous Americans have been copying the trews and dinner jacket pairing at least as far back as 1950 according to a Life magazine article from April of that year:
For country-club clansmen who don’t want to leave their tartans home, Chipp [a New York tailor], whose plaid apparel ranges from garters to golf slacks, is turning out cummerbunds, jackets and “trews” that can be worn dining out.
Trews are even more informal than the tartan dinner jacket as they lack the silk trim that characterizes evening suits. Therefore their use (by non Scots) should be confined to the most informal of formal occasions, namely a private dinner at home or the club, and they should always be worn with standard black-tie accessories. It also probably wouldn’t hurt to observe the etiquette described in the same 1950 Life article: “They are worn only by a host, never by a guest.”