bikini state

Established on this day in 1970 and in use until 2006 before being replaced by a more general and public terror alert status system, the eponymous indicator—which the Ministry of Defence says is a random and meaningless choice by a computer (see also)—was similar to counterparts in other countries though levels were determined by the threat to the institution and organisation itself rather than a generalised contingency plan.
Starting with Code White, the least serious and thus never invoked during the history of the BIKINI state, meaning no information available / “situation stable,” black meaning the possibility of an act with targets being undefined and alternately the potential for civil unrest with public safety questionable, Black Special, an increased likelihood of attack, Amber, a substantiated threat with a specific target or a transition to war, and Red signifying that the UK is at war with attacks imminent. The public became acquainted with the scheme through the 1984 apocalyptic war drama Threads.