§ Mr. MacdonaldTo ask the Secretary of State for Defence what is his Department's assessment as to the proportion of time during which at least one Trident submarine could not he guaranteed to be on station if only three Trident submarines were procured.
§ Mr. Archie HamiltonI am unable for reasons of security to give details of my Department's assessment. However, I can say that a three-submarine force could not guarantee the presence of at least one submarine on station at all times. Continuity of operations is essential to the maintenance of a credible strategic deterrent, and has been our policy throughout the life of the Polaris force. It follows, therefore, that the planned Trident force must comprise four submarines if an effective deterrent is to be maintained.