Blue Peacock, renamed from Blue Bunny and originally Brown Bunny, was a British tactical nuclear weapon project in the 1950s.
The project's goal was to store a number of ten-kiloton nuclear mines in Germany, to be placed on the North German Plain and, in the event of Soviet invasion from the east, detonated by wire or an eight-day timer in order to "...not only destroy facilities and installations over a large area, but ... deny occupation of the area to an enemy for an appreciable time due to contamination..."
The design was based on the free-falling Blue Danube, but the Blue Peacock weighed 7.2 long tons (7,300 kg). There would be two firing units: the casing and the warhead. Its steel casing was so large that it had to be tested outdoors in a flooded gravel pit near Sevenoaks in Kent. Since the bomb would be unattended, anti-tamper devices were also used. The casing was pressurized, and pressure and tilt switches were added. There were three different ways that the bomb could be detonated: a wire located three miles (4.8 km) away, an eight-day timer, or anti-tampering devices. Once armed, Blue Peacock would detonate ten seconds after being moved, if the casing lost pressure, or if it was filled with water.
The project was developed at the Royal Armament Research and Development Establishment (RARDE) at Fort Halstead in Kent in 1954.
In July 1957 the British Army ordered ten Blue Peacocks for use in Germany, under the cover story that they were atomic power units for troops in the field. In the end, though, the Ministry of Defence cancelled the project in February 1958. It was judged that the risks posed by the nuclear fallout and the political aspects of preparing for destruction and contamination of allied territory were too high to justify.
One technical problem was that during winter buried objects can get very cold, and it was possible the mine's electronics would get too cold to work after some days underground. Various methods to get around this were studied, such as wrapping the bombs in insulating blankets. One particularly remarkable proposal suggested that live chickens be included in the mechanism. The chickens would be sealed inside the casing, with a supply of food and water; they would remain alive for a week or so. Their body heat would, it seems, have been sufficient to keep the mine's components at a working temperature.
This proposal was sufficiently outlandish that it was taken as an April Fool's Day joke when the Blue Peacock file was declassified on 1 April 2004. Tom O'Leary, head of education and interpretation at the National Archives, replied to the media that, "It does seem like an April Fool but it most certainly is not. The Civil Service does not do jokes."