Analysis of information sources in references of the Wikipedia article "Red Snow" in English language version.
Red Snow is the British version of the U.S. Mk.28, which has been tested by the American Authorities. It follows that all current British nuclear weapons are based on tested designs.
PETER – A boosted fission device, an anglicised copy of the W-34 Python primary used in the Red Snow strategic warhead and it was already in production in the UK, so could be available quickly. Yield of 11 kt was not capable of enlargement to the sizes specified by OR.1176 / 1177.
Red Snow is the British version of the U.S. Mk.28, which has been tested by the American Authorities. It follows that all current British nuclear weapons are based on tested designs.
PETER – A boosted fission device, an anglicised copy of the W-34 Python primary used in the Red Snow strategic warhead and it was already in production in the UK, so could be available quickly. Yield of 11 kt was not capable of enlargement to the sizes specified by OR.1176 / 1177.