To ask the Secretary of State for Defence what recent assessment he has made of the number of (a) air-launched and (b) submarine-launched cruise missiles required to constitute a deterrent threat comparable to that of a Vanguard-class submarine; and what recent assessment he has made of the vulnerability of cruise missiles to destruction prior to reaching their targets. (275084)

Assessments of submarine and air launched cruise missile systems were made as part of the supporting evidence for the December 2006 White Paper “The Future of the UK’s Nuclear Deterrent” (Cm6994). No cruise missile launched system was considered to be as capable as a ballistic missile based deterrent. Cruise missiles are more vulnerable to interception, largely because of their slower speed and lower trajectory.

To ask the Secretary of State for Defence (1) what the maximum range is of (a) the Trident D5 ballistic missile and (b) a submarine-launched cruise missile; and if he will make a statement; (275085)

The maximum range of a Trident D5 missile is approximately 6,000 nautical miles, and that of the UK's submarine launched Tomahawk cruise missile is approximately 1,000 nautical miles.

The maximum number of warheads that can be carried on a single Trident D5 missile is 12. The UK does not possess nuclear armed cruise missiles. The options described in the 2006 White Paper “The Future of the UK’s Nuclear Deterrent” (Cm6994) assumed that if the UK procured a nuclear armed cruise missile, then one warhead would be carried on each missile.

To ask the Secretary of State for Defence what recent assessment he has made of the capability of a state under attack from cruise missiles to determine prior to impact such missiles are armed with (a) conventional and (b) nuclear warheads. (275087)

The UK keeps the capabilities of cruise missiles from countries of concern, including the types of warhead, under continual review. We judge that to determine the type of warhead whilst the missile is in flight is not currently possible. However, if the state under attack has prior knowledge of the aggressors’ cruise missile capabilities, the type of warhead may already be known.