British Defense Secretary Grant Shapps and other top officials were present on a Royal Navy nuclear submarine during a test-firing of a Trident II 5 nuclear missile that failed last month. The incident occurred on January 30 when the missile crashed back into the sea close to the submarine HMS Vanguard off the coast of Florida. This marked the second misfire of a Trident test by the Royal Navy, with a previous incident in 2016 where a missile veered off course and was destroyed. Shapps confirmed the recent failure in a statement to parliament on February 21.

Accompanying Shapps onboard HMS Vanguard were Britain's top sailor, Adm. Sir Ben Key, as well as Defence Procurement Minister James Cartlidge and senior unnamed U.S. officials. The Sun newspaper reported that the misfire was due to the first-stage boosters of the missile failing to ignite. Despite this, Shapps assured lawmakers that the incident was event-specific and would not affect the reliability of the wider Trident missile systems.

The U.S. Navy, which also operates the Trident D5 missiles, had a successful test-firing last September, in contrast to the recent British misfire. However, Shapps confirmed that the submarine and crew of HMS Vanguard were successfully certified and would rejoin the operational cycle as planned. Vanguard is part of a fleet of four nuclear missile-armed submarines, with one being at sea and operational at all times. Plans for replacing the aging submarine fleet with the Dreadnought-class boats are underway, with construction expected to start in the early next decade.