"To conserve vital stocks, Ted Heath's Government put industry on a three-day week from 1 January 1974. There was no legislation: industry simply did as it was told in that very different period in our history. Under the Government's restrictions, a 50 m.p.h.speed limit was imposed on motorists. Television closed down at 10.30 p.m. A junior minister (subsequently a member of Margaret Thatcher's Cabinet) earned instant notoriety by advising people to clean their teeth in the dark."
I love the cleaning the teeth in the dark story.