HMS Vanguard, one of the four Trident submarines that maintain the UK’s nuclear deterrent, left Devonport yesterday after a very much delayed Long Overhaul Period and Refuel (LOP(R)).

During Vanguards’s first 35-month LOP(R) which took place between Feb 2002 and Jan 2005, she received the new Core H reactor. This new core design, which has subsequently been installed in her sister boats and on the Astute class submarines from the outset, was intended to avoid the need to refuel at all during its lifetime. Vanguard is therefore the first submarine to have a Core H refuelling, a task that was not envisaged when it was designed.

Vanguard will return to Faslane for workup before resuming deterrent patrols later this year.