To ask the Secretary of State for Defence what the planned lifespan is of the existing generation of Trident missile warheads; what recent consideration he has given to the practicability of extending that lifespan; and if he will estimate the likely savings to the public purse of undertaking such an extension instead of procuring a replacement system. (284420)

The UK’s existing nuclear warhead design is likely to last into the 2020s, although we do not yet have sufficient information to judge precisely how long we can retain it in service. We are currently undertaking detailed studies to assess this and potential options for replacement should that be necessary. It is too soon to estimate the precise timing and the potential costs of any options beyond the £2-3 billion estimate, at 2006-07 prices, given in the 2006 Defence White Paper.