Operating posture of the UK's
nuclear deterrent
11. The 1998 Strategic Defence Review (SDR)
stated that the UK would continue to maintain continuous-at-sea
deterrent (CASD) patrols. This meant that one of the UK's four
Vanguard-class submarines would be on patrol at any give time.
The SDR stated that the purpose of CASD was "to avoid misunderstanding
or escalation if a Trident submarine were to sail during a period
of crisis".[7] By
keeping one submarine on patrol at all times, the UK avoids the
risk of sending incorrect or misleading signals to a potential
adversary at times of heightened alert. In our first report on
the future of the UK's strategic nuclear deterrent, we suggested
that if the MoD believed the UK should retain the continuous-at-sea
deterrent cycle, it must either extend the life of the Vanguard-class
submarine or procure a new platform to be in service by around
2020. The issue of maintaining continuous-at-sea deterrence is
at the heart of the debate over the timing of decisions on the
future of the UK's nuclear deterrent.
12. According to the MoD, a four boat fleet is normally
required to guarantee one boat on patrol at all times, because
one boat is either preparing to enter refit, in refit, or leaving
refit and preparing to re-enter service, one is in maintenance
between patrols, and one is either on its way to take up patrol
or returning from patrol. By the time Vanguard goes out-of-service
the last refit will have been completed, and so it will only be
when Victorious goes out-of-service in 2024 that the MoD
says the continuous-at-sea regime could not be sustained.
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