British control of Polaris within NATO strategy

Did Britain retain national control of its Polaris deterrent even though the force served NATO strategy?

Yes. Britain retained ultimate control, while the Polaris force's primary operational commitment was to NATO.

Alliance planning did not change who controlled Britain's ultimate deterrent. Speed confirms that national authorities retained control of the Polaris submarines. Their planned strategic role, however, was committed primarily to NATO in the first instance. The short exchange separates sovereign release authority from the alliance mission assigned to the force. That distinction is essential when reading claims that a nuclear capability is both national and integrated into collective defence.