Oops, sorry, my mistake. HMCC Valiant is not a nuclear warship at all, but some kind of love boat for retired VAT Inspectors, as this description I found on the web confirms:
HM Customs Cutter Valiant
Special care has been taken to provide a high standard of living accommodation for the crew during operations. Low noise levels and a relaxation area for those off-watch reduces crew fatigue. The large, well-equipped galley is designed to enable the crew to prepare meals and drinks in all sea conditions.
Enjoy the casino, chaps!