We do not routinely calculate the operating cost of specific committed or contingent force elements in support of the deterrent, and such estimates are necessarily illustrative. The answer that my right hon. Friend the Member for Kilmarnock and Loudoun (Des Browne), as Defence Secretary, gave to the hon. Member on 8 March 2007, Official Report, column 2131W, estimated the annual operating costs of committed conventional force elements to be around £25-30 million. We have not prepared a more recent estimate as to do so would incur disproportionate costs.
The current Trident II D5 missile is expected to remain in service until 2042. No expenditure has been incurred on a successor to the Trident II D5 missile.
As set out in the 2006 White Paper, we estimate that the procurement costs of the replacement for the current Vanguard class submarines will be between £11-14 billion at 2006-07 prices. The total spent on the replacement submarine and associated propulsion system since the beginning of April 2007 to the end of June 2009 is some £250 million.
Work is ongoing to assess whether continuous at sea deterrence could be achieved with a three boat fleet, and at what cost.