Question to the Ministry of Defence:

To ask the Secretary of State for Defence, what estimate he has made of the additional costs of maintenance and other in-service costs that will be incurred by retaining the Vanguard submarines in service for approximately five years longer than envisaged in the 2010 Strategic Defence and Security Review.

As set out in the 2010 Strategic Defence and Security Review, we have assessed that we can safely manage and maintain the Vanguard boats until the Successor submarines are introduced into service in the early 2030s. The marginal costs associated with maintaining the submarines can be contained within the existing running cost of the deterrent, which is around 6% of the defence budget per year.