Glen plaid (short for Glen Urquhart plaid) or Glenurquhart check is a woollen fabric with a woven twill design of small and large checks. It is usually made of black/grey and white, or with more muted colours, particularly with two dark and two light stripes alternate with four dark and four light stripes which creates a crossing pattern of irregular checks. Glen plaid as a woven pattern may be extended to cotton shirting and other non-woollen fabrics.
The name is taken from the valley of Glenurquhart in Inverness-shire, Scotland, where the checked wool was first used in the 19th century by the New Zealand-born Countess of Seafield to outfit her gamekeepers, though the name glen plaid does not appear before 1926
Tweed suit with plus fours from Dashing Tweeds. Photograph: Dashing Tweeds
( By the way, definitely wrong shoes for plus fours breeches / Jeeves )