17a
Treble One - The SIOP is the US national nuclear war plan. The UK nuclear deterrent was/is assigned to NATO along with the other nuclear armed NATO countries (including those US forces assigned to NATO). The NATO plan would have been carried out in conjunction with the US SIOP.
Peter Hennesay's new book on the British nuclear submarine fleet and it was the same for the V Force that the deterrent was able to be used by the RAF/RN for national issues. Polaris and Trident come under the Bermuda Agreement signed by McMillan and Kennedy.
WE 177 was all British in design development and deployment whilst integrated into the NATO war plan.