WE.177A

WE.177 was the designation of a range of tactical and strategic nuclear bombs used by the British Armed Forces.

There were three versions; WE.177A was a boosted fission weapon, while WE.177B and WE.177C were thermonuclear weapons. All could be delivered by fixed-wing aircraft and also, in the case of the WE.177A in anti-submarine mode, by helicopters and by the Ikara missile system. All types could be parachute retarded.

The first version to be fully deployed, WE.177B, was delivered to the Royal Air Force in September 1966 followed by deliveries of the WE.177A to the Royal Navy beginning in 1969, and the RAF in 1971, after a delay caused by the need to produce the ET.317 warhead for the UK Polaris A3T first; and was followed by WE.177C deliveries to the RAF. The Navy weapons were retired by 1992 and all other weapons with the RAF were retired by 1998.

The WE.177 was the last nuclear bomb in service with the Royal Air Force and the last tactical nuclear weapon deployed by the UK.

In May 1960 Prime Minister Harold Macmillan signed an agreement with President Eisenhower to purchase 144 AGM-48 Skybolt missiles for the V bomber force. Along with the missiles, the UK would receive the design of the Skybolt's W59 warhead, which was much smaller and lighter than even the smallest UK designs of the era. The UK version would be known by the codename RE.179.

However, the W59 primary used PBX-9404 and was considered by the British to be unsafe due to the potential for shocks to set off the PBX. Since the late 1950s they had been working on their own primary design, originally "Octopus" and then "Super Octopus", that used more explosive and less fissile material, and was shock-insensitive as well. They proposed adapting the Super Octopus design for use in RE.179, calling the new version "Cleo". Cleo designs were tested underground at the Nevada Test Site in 1962. The secondary (or fusion elements) of RE.179 remained identical to the W59's, and were known as "Simon" in WE.177B and as "Reggie" in the ET.317 version for UK Polaris.

...
Wikipedia