Dad's Army (1968)

Season 6: Episode 3

Mainwaring gathers his troops for the secretive reading of top-secret orders, concerning the passage – no actual stop – of the royal train. The mood darkens when everyone else already seems in on the secret. Alas, a regular train breaks down before the royal train, and a pills mix-up incapacitatee its staff. The platoon's ill-considered rescue attempt soon devolves into a potential real disaster.