Dr Julian Lewis: I welcome the update to Parliament on the United Kingdom’s future nuclear deterrent published today, which states:

“The Government policy remains to maintain a continuous at sea deterrent and proceed with the programme to build a new fleet of ballistic missile submarines.”

Will the Secretary of State confirm that the Government will in no way entertain any squalid deals with any other party if what is needed for continuous-at-sea deterrence is four submarines and if another party, conceivably the Liberal Democrats, tried to argue that three would do?

[The Secretary of State for Defence (Mr Philip Hammond): My hon. Friend may note that some people have even suggested that two submarines could provide some sort of deterrent, but the Government and the Prime Minister have made clear their commitment to continuous-at-sea deterrence and to delivering the number of submarines required to provide proper at-sea deterrence, not some jumped-up, import alternative.]