This is the same sub class the UK used to shoot a D5 warhead at the United States by "accident" in 2016
>The unshakeable reliability of Britain’s submarine-based nuclear deterrent has been called into question after a Trident II D5 ballistic missile reportedly veered off course during a test last year.
>Vanguard-class submarine HMS Vengeance launched the unarmed missile during a post-refit demonstration and shakedown operation (DASO) off Florida in June 2016.
>Media reports suggested that a navigational error may have occured and that the missile steered towards the U.S. east coast instead of continuing its intended course over the Atlantic Ocean towards Africa.
https://news.usni.org/2017/01/25/royal-navy-trident-missile-malfunction-prompts-claims-u-k-government-cover
https://www.thetimes.co.uk/article/no-10-covered-up-trident-missile-fiasco-hch3shsrn