British Prime Minister Tony Blair has declared that British possession of strategic nuclear weapons is crucial for long-term national strategic interests. The problem is that the British nuclear deterrent has never been truly independent. Originally both British and American atomic weapons were subject to one another's veto, under the terms of the 1943 Quebec Agreement on Tube Alloys. (Tube alloys was the term used to conceal the true nature of the Manhattan Project.) However, a combination of American legislation and straitened British economic circumstance put paid to any independent tube alloy ambitions for the British armed forces. The matter wasn't really of any significance until after the U.S. Air Force had based its strategic bombers in Britain again in July 1948, and both America and Britain were fighting together once again, in the Korean peninsula, after the North Korean invasion in June 1950. The National Security Archive at George Washington University has published a series of documents about the relationship between American nuclear weapons and British governments.
Britain's first atomic deterrent, a bomb delivered by an aircraft, entered service in November 1953. By this stage, NATO had come into existence, and in the circumstances targets for British weapons were likely to be determined by the alliance's command, a situation that was formalized in 1962 by the Athens Guidelines, paragraph 5. Thus, the concept of an independent British nuclear deterrent has always been more of a de jure than a de facto one.