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Dockyard History11th March 2024

Nuclear Bomb and The Historic Dockyard Chatham

HMS CAVALIER with nuclear hydrogen bomb mushroom cloud.

With Oppenheimer back in the news due to its film awards success, it brings with it renewed interest in the history of nuclear weapons.
One lesser-known association is that of The Historic Dockyard Chatham with nuclear testing in the late 1950s.

Who is J. R. Oppenheimer and what was his role in the Development of Nuclear Weapons?

The film Oppenheimer is based on the life of J. Robert Oppenheimer, who is considered to the father of the atomic bomb due to his position as the Director of Project Y for the Manhattan Project.

The Manhattan Project was an organisation of research and development during the Second World War that advanced nuclear reactions as a weapon. It was led by the United States in collaboration with the United Kingdom and supported by Canada. It is synonymous with the nuclear bombs dropped on Hiroshima and Nagasaki in Japan that brought about an end to the Second World War.

The two types of bombs that were dropped; ‘Little Boy’ (gun-type fission weapon) fell on Hiroshima whilst ‘Fat Man’ (implosion-type) targeted Nagasaki, both were developed simultaneously at Project Y / Los Alamos Laboratory under the direction of Oppenheimer.

After the War

J. Robert Oppenheimer and The Manhattan Project brought about the end of six years of conflict and destruction that defined the Second World War. However, it did not end the fascination with nuclear reactions such as explosions and the desire to build more destructive nuclear weapons.

What followed was an era defined by the Cold War and a race (particularly between the United States and the Soviet Union) to become the most advanced nation to hold nuclear weapons.

For its part, the United Kingdom undertook several nuclear tests in the 1950s. Having started a development programme during the Second World War that eventually combined with the United States. In January 1947, a cabinet sub-committee voted to resume the country’s programme to develop and build nuclear weapons.

The first British nuclear weapons test was Operation Hurricane which took place on 3 October 1952. This resulted in Great Britain becoming the third global nuclear power after undertaking a successful detonation of a plutonium implosion device.

British Nuclear Tests

In total, there were 21 nuclear tests spread across six operations between 1952 and 1958.

Operation Hurricane was the first nuclear test, followed by Totem (1953), Mosaic (1956), Buffalo (1956), Antler (1957), Grapple (1957 – 58), and the Nevada Test series (1961 – 1991). With the exceptions of Operation Grapple and the NTS series, all tests were undertaken in Australia. The NTS series was carried out in the Nevada desert surrounded by mountains.

Operation Grapple was the largest nuclear test undertaken by the British government and took place in the Pacific Ocean, more accurately Malden Island and Kiritimati (formerly Christmas Island).

Chatham Dockyard and Operation Hurricane

Operation Hurricane was carried out at the uninhabited Monte Bello Islands, situated approx. 50 miles from the Western Australian coast.

A Task Force of five Royal Navy ships, HMS PLYM, HMS NARVIK (ex LST3044), HMS CAMPANIA, HMS TRACKER (ex LST 3522) and HMS ZEEBRUGGE (ex LST 3532) supported the test.

HMS PLYM, NARVIK and CAMPANIA all had links to Chatham Dockyard. Mentions can be seen in the ‘Ships in Dry Dock’ ledger that is held within The Historic Dockyard Chatham’s archive which confirms they all underwent repairs or refits at Chatham ahead of Operation Mosaic.

HMS PLYM was selected to be the test ship for the operation, chosen from the Reserve Fleet due to being ‘an expendable ship.’ Arriving in Chatham in July 1952 she underwent a conversion refit for ‘Special Compartments’. The conversion consisted mainly of stripping out redundant electrical junction boxes, distribution boxes, cabling, and sockets, and fitting new items and cabling required for the test.

HMS PLYM was re-commissioned at Chatham on Tuesday 19th February 1952. However, conversion work continued, either in Chatham or elsewhere on the River Medway. PLYM sailed from Chatham on Wednesday 4th June with a skeleton crew of 102 and arrived at Monte Bello Islands on 8th August 1952.

The test required a 25-kiloton atomic bomb to be detonated within the hull of HMS PLYM, resulting in the ship being vaporised.


The second Chatham-associated ship to be involved in the British nuclear tests was HMS NARVIK. In 1947, NARVIK was converted from a Landing Ship Tank LST 3044 into a Landing Ship Carrier. For Operation Hurricane, she was used as the Health Ship, and as such was extensively equipped with decontamination facilities, her role also included technical control and monitoring.

After the test HMS NARIVK returned to Chatham. Her return was reported in the press with the comment “At Chatham a Royal Naval squad checked the vessel with Geiger counters for any traces of radio activity”.

HMS NARVIK continued to have a prominent role in Britain’s nuclear tests; she reprised the role of control ship for Operation Grapple, but it also participated in Operation Mosaic. After Mosaic, she had very little time to return to the Chatham Dockyard for a refit before heading out to Christmas Island for Grapple.

The final ship, HMS CAMPANIA was an Escort Carrier. In 1951 she was refitted at Chatham, in No 9 Dock on St Mary’s Island, for the role of Flagship at the Atomic Test at Monte Bello Islands. Her role included acting as the main base for the test but proved to be unsuitable for the role. This was the result of hot and cramped conditions on board, as well as insufficient small boats available to carry the 85 scientists onboard from ship to shore.

Site for the Hydrogen Bomb

Following the successful tests of Totem (1953), Mosaic (1956), Buffalo (1956), and Antler (1957) British scientists set their sights on developing larger, more destructive weapons. This would contravene the existing agreement with the Australian government.

Operation Grapple consisted of four series of nuclear tests carried out in Kiribati. It was the first time that the British tested the Hydrogen Bomb. The explosive yield of Operation Grapple had a total yield of 7,869 kilotons; a sensational amount considering that the combined total yield of all tests from Hurricane to the NTS series was 9,282 kilotons.

Previous nuclear testing sites in Australia were agreed with the Australian government under the agreement that no thermonuclear testing would take place. The tests were proving to be controversial with Australians, resulting in the Australian Minister for Supply, Howard Beale, stating that “the Federal Government has no intention of allowing any hydrogen bomb tests to take place in Australia. Nor has it any intention of allowing any experiments connected with hydrogen bomb tests to take place here.”

Following conversations with Prime Minister Anthony Eden and Australian Prime Minister Robert Menzies, a new testing site was to be found.

Locations in the South Pacific, Antarctica, and New Zealand were considered with the Kermadec Islands, which lie about 1,000 kilometres (620 mi) northeast of New Zealand being favoured by the government. They went as far as writing to the New Zealand Prime Minister Sidney Holland requesting permission, but it was refused.

It was settled that Kiritimati (Christmas Island) was chosen as the base for Operation Grapple and its tests of the hydrogen bomb. The Island was remote as it sits 1,335 miles (2,148 km) from the nearest populated city, Honolulu. The island did have a small population of 260 that worked the island’s coconut plantation.

Operation Grapple

Operation Grapple was a series of atmospheric nuclear tests. Previous nuclear tests had tested atomic weapons, but Grapple moved to detonate hydrogen bombs. During the operation, Chatham ship HMS NARVIK reprised its role as a control ship.

The initial Grapple series consisted of three tests (Grapple 1, Grapple 2, and Grapple 3) over Malden Island. Grapple 1 took place on 15th May 1957 and had a yield of 300 kilotons; Grapple 2 on 31st May 1957 with a 720-kiloton yield; Grapple 3 on 19th June 1957 with a 200-kiloton yield.

Subsequent tests moved from Malden Island and happened closer to Kiritimati. These tests were Grapple X (8th November 1957; 1800-kiloton yield); Grapple Y (28th April 1958; 3000-kiloton yield); Grapple Z1 (22nd August 1958; 24-kiloton yield); Grapple Z2 (2nd September 1958; 1000-kiloton yield); Grapple Z3 (11th September 1958; 800 kiloton yield); Grapple Z4 (23rd September 1958; 25-kiloton yield).

By comparison, ‘Fat Man’ that fell on Nagasaki had a yield of 25 kilotonnes and ‘Little Boy’ that dropped on Hiroshima had a yield of 15 kilotonnes.

The detonation undertaken during Grapple Y remains the largest British nuclear weapon ever tested. The weapon had an explosive yield of about 3 megatons of TNT and is considered a true hydrogen bomb.

HMS CAVALIER and Operation Grapple

The Historic Dockyard Chatham’s very own HMS CAVALIER was present during the largest nuclear test of Operation Grapple; Grapple Y that took place in April 1958.

Whilst not a part of the inner cluster of ships, CAVALIER was present at Christmas Island between March to May 1958 and undertook a role as an intruder patrol ship. She watched the seas for passing ships and warned them to steer clear of the test area, her additional was to provide air-sea rescue if the need arose. As detailed in the official GRAPPLE Y and Z: RAF/AWRE operation orders located in The National Archives Kew, however, there are contemporary accounts of HMS CAVALIER also undertaking weather monitoring activities.

In Barry Knell’s The Fastest Ship in the Fleet, he details the crew’s experience during Operation Grapple:
“The crew was ranged on the upper deck; they heard the roar of a distant Valiant bomber and saw its contrails.
‘Make sure your neck is covered and adjust each other’s goggles correctly’. Forty seconds to go; ‘Sit with your back to the blast and do not turn around until you are told’. “

The resulting explosion was described as a “great awesome inferno in the sky, black and red and growing, evil yet beautiful, growing into a white and red monstrous fungus reaching thousands of feet high.”

After the test, men were warned not to swim in the sea or eat the fish but there are accounts of crew members netting the dead fish and eating them for dinner.

After being released from Operation Grapple Y, HMS CAVALIER carried on through the Suez Canal and then to Singapore for a refit.


After being decommissioned in 1972, HMS CAVALIER was laid up in Portsmouth, before moving down the coast to Southampton. In August 1982, she briefly opened as a museum but was moved to Brighton in October 1982.

In 1987, the ship made its long journey up north to Tyneside to form the centrepiece of a newly proposed national shipbuilding exhibition centre to be held in the former shipyard of Hawthorn Leslie and Company. The proposed exhibition never materialised, and she sat in dry dock until being sold in 1998 to the newly formed Cavalier Trust.

HMS CAVALIER arrived at The Historic Dockyard Chatham on 16 May 1999 and sits proudly in No. 2 dry-dock.

Due to CAVALIER’S age and the shipbuilding practices of the time, she is regularly tested by trained professionals. Everything within public access is safe and does not pose any health risks.

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