Anyone seeking a more in depth treatment of the Polaris\Chevaline and Trident story along with a description of the targeting options considered may wish to refer to The Silent Deep by Hennessy and Jinks with particular reference to Ch8 Maintaining The Deterrent: From Polaris to Trident.
As a matter of interest, I have long sought a similar account in English of parallel developments and debates on the French SLBM program. It seems less well publicly documented.
YS