To ask the Secretary of State for Defence how many Trident submarines there are in the Trident programme; how many have been acquired; and how many are on station at any given time. 
There are four submarines in the Trident programme; so far two have entered service. It is not our practice to give details of the dispositions of the strategic nuclear deterrent.
To ask the Secretary of State for Defence when his Department expects to commission the last Trident submarine in its programme. 
HMS Vengeance, the fourth Trident submarine, will enter service around the turn of the century.
To ask the Secretary of State for Defence what will be the additional contribution of the last Trident submarine to the United Kingdom's nuclear deterrent capability. 
The four boat Trident fleet will guarantee continuous deterrent patrols throughout the planned 25-year life of the submarines, which includes periods for refit.