The Swiftsure Class of six submarines were commissioned at regular intervals between 1972 and 1981 and the commissioning date for each boat is listed as follows. Due to the long period of time that has since elapsed, the unit cost of these submarines is no longer held centrally and could be provided only at disproportionate cost.<Table width="100%" summary="" cellspacing="3" cellpadding="3" border="0"><TR><TD>Swiftsure class</TD><TD>Commissioning dates</TD></TR><TR><TD>HMS Swiftsure</TD><TD>17 April 1973</TD></TR><TR><TD>HMS Sovereign</TD><TD>11 July 1974</TD></TR><TR><TD>HMS Superb</TD><TD>13 November 1976</TD></TR><TR><TD>HMS Sceptre</TD><TD>14 February 1978</TD></TR><TR><TD>HMS Spartan</TD><TD>22 September 1979</TD></TR><TR><TD>HMS Splendid</TD><TD>21 March 1981</TD></TR></Table>