English Heritage's book "Cold War" comments that -
"..recent research has shown that no more than 20 Blue Danube warheads were functional between 1957 and 1961." and "..that the capacity of the stores far exceeded the number of warheads" and speculates "...may have been part of a deadly game of nuclear brinkmanship to mislead the Soviets about the size, location and readiness of the British stockpile."