A US test launch of Trident: the failed British test occurred in June last year

A serious malfunction in Britain’s Trident nuclear weapons deterrent was covered up by Downing Street just weeks before the crucial House of Commons vote on the future of the missile system.

The Sunday Times can reveal that a Trident II D5 missile — which can kill millions when armed with nuclear warheads — experienced an alarming failure after being launched from a British submarine off the coast of Florida in June last year.

It was the only firing test of a British nuclear missile in four years and raises serious questions about the reliability and safety of the weapons system. The failure prompted a news blackout by Downing Street that has remained in place until this weekend.

Failure to disclose the error was described as