In the event of a SUBSUNK emergency at sea, Vanguard Class. SSBNs can function as a mother ship in the MOSUB role and can carry a Deep Submergence Rescue Vehicle (DSRV) that can. mate with all RN submarines and most modern submarines fitted with diver lockout hatches. HMS Victorious was used to prove the concept and the piggy-back installation for this important role whilst at Barrow.
HMS Vigilant
The third boat, SSBN07, was officially ordered on November 13th 1990, formally laid down on February 16th 1991, launched by shiplift on October 14th 1995 and commissioned on November 2nd 1996.