Archival documents reveal British H bomb was developed in Australia despite denials

Jun 27, 2021

Documents found in the National Archives reveal previously ignored proof that promises made by the UK not to test thermonuclear weapons in Australia were broken.

In June 1956 the UK was moving from atomic to thermonuclear weapons development in its test programme in Australia, despite repeated promises not to do so. The duplicity of those promises is revealed in two documents I have recently found online in the National Archives of Australia. These documents were ignored by both the Australian and UK official histories of the tests and by the Royal Commission into British Nuclear Tests in Australia despite having been supplied to them.

Throughout 1954 the archival documents state several that ‘there would be no question of testing thermonuclear weapons in Australia.’

For instance, on 18 February 1955 ‘Her Majesty’s Government wish to state categorically that there has never been any suggestion that a hydrogen bomb should be tested in Australia.’ A 1955 letter from Australian Prime Minister’s Department Department to the UK High Commissioner in Canberra restates ‘Hydrogen weapons will not be tested at the site’ [Maralinga].

On 18 February 1955 it was stated that ‘In view of statements which have appeared in the Press Her Majesty’s Government wish to state categorically that there has never been any suggestion that a hydrogen bomb should be tested in Australia.’

On February 22, 1955 it was reported that Australian Minister for Supply Howard Beale ‘concluded by repeating his earlier assurances that no hydrogen bomb tests or any tests of that character would be carried out.

For a few hours it seemed as though Beale was winning the argument. In the first week of April a telegram from the Commonwealth Relations Office in Downing Street to the UK High Commissioner in Canberra proposed that

‘Though terms of assurance at the end of the statement merely repeat what has already been said by Mr. Beale, we suggest that a preferable wording would be “no hydrogen weapon test or tests of that magnitude will take place”. This wording is in accordance with Memorandum of Arrangements [being drafted for Maralinga] which precludes all hydrogen weapon tests not only bombs. The use of the word “magnitude” recognises Australian control over explosive yield from any test that it is agreed should be undertaken but if Australians prefer to repeat wording of previous announcement we would not press amendment.’ It was stated that the UK would use the term magnitude even if Australia didn’t – ‘No hydrogen weapon test or tests of that magnitude will take place in Australia.’

Testing the triggers to initiate a thermonuclear bomb

But parallel with these verbal parries, the Australian government permitted ‘minor trials’ of triggers or initiators for the H bomb that the scientists were rushing to build for its scheduled detonation in May 1957 before the expected ban on atmospheric testing. The test site was one corner of the proposed ‘permanent proving ground’ of Maralinga. The ‘Kittens’ initiator tests of 1955 involved conventional high explosives and 150lb of natural uranium and resulted in significant contamination of the immediate firing range.

On April 20, 1955 a UK memo stated ‘As far as we know the initiator programme is still unchanged’. It has already been announced here that these minor tests are to take place. Originally Mr Beale hastily assured the press that these would not be in any way related to the hydrogen bomb. This was incorrect and he has since covered himself by saying that there will be no ‘hydrogen bomb test or tests of that nature and magnitude’.

Sudden need for a second test round at the Monte Bellos

Even as the Maralinga Memorandum was being negotiated in 1955 the UK Minister for Supply was asking the Australian Government for an unexpected ‘programme of two firings in the Monte Bellos’ in April 1956.

The typescript of the Australia Minister for Supply Beale’s announcement of the Maralinga Agreement states ‘As I have said before, no hydrogen or similar types of bombs will be exploded in Australia.’ It was dated 4 May, 1955 the same day as the request was being drafted in London.

Another memo that same day from the UK Minister of Defence to the Foreign Secretary stated that:

‘As an important step towards full-scale test of thermonuclear weapons, the Atomic Weapons Research Establishment wish to carry out certain experiments in April 1956. These will take the form of atomic explosions, the yields of which will be boosted by the inclusion of light elements… in the Monte Bellos.’

There may be some difficulty with the Australians, in view of the definite statement made by the Australian Minister for Supply that no thermonuclear tests would be carried out in Australia. These experiments will, however, not be tests of thermonuclear weapons and their yield will not be more than 2½ times that of the weapon which we exploded in the Monte Bello Islands in 1953 [the year should have been 1952].’

If that were the case, there should be no ‘difficulty with the Australians.’ But Australian officials, not least in Menzies’ Prime Minister’s Department, were beginning to suspect – because of the addition of thermonuclear ‘booster’ light elements deueterium, tritium and lithium – that ‘something approaching an H bomb’ was planned despite all the denials.

British Prime Minister Eden told Prime Minister Menzies on 16 May 1955 that ‘Experiments would consist of atomic explosions with inclusion of light elements as a boost. It would, of course, be made clear in any public announcement that explosions were atomic and not thermonuclear.’

A concurrent message from Menzies’ Prime Minister’s Department made reference to ‘full scale’ to be carried out in 1957.

On 21 July 1955 a memo from the Commonwealth Relations Office in Downing Street to the UK High Commissioner in Canberra instructed:

‘We certainly wish knowledge that there will be full scale tests in 1957 and connection between them and subject of Mr. Menzies’ message be limited to absolute minimum number of individuals.’

The reference was to a June 1955 message about the requested Monte Bellos/Mosaic tests in mid 1956.

The UK Secretary of State for Commonwealth Relations the Earl of Home toured Australia for a month from mid September 1955. His briefing papers inform him of the tangled web he would need to negotiate in relation to the proposed testing at the Monte Bellos:


6. At an early stage in the negotiations with the Australian Government Mr. Beale, the Australian Minister for Supply, made categoric statements, without first consulting us, to the effect that the Australian Government had no intention of allowing H-bombs or any related experiments to take place in Australia. He subsequently modified the last portion to ‘hydrogen bomb tests or any tests of that character’.  Mr. Beale has, however, shown himself to be extremely sensitive over the possibility of any thermo-nuclear weapon testing in Australia.


7. We are anxious to carry out two experimental firings consisting of atomic explosions with the inclusion of light elements as boost. The information obtained from these trials should be a vital link in the development of the thermo-nuclear weapon.. We wish to carry out these trials next April, before Maralinga will be ready. We had agreed with the Australian Government that we would not test thermo-nuclear weapons in Australia but Mr. Menzies has nevertheless agreed to the firings taking place in the Monte Bello Islands (off the North-West coast of Western Australia), which have already been used before for atomic tests. As already explained, the Australians are very sensitive on the question of thermo-nuclear explosions, and although although the true character of these tests is understood by the authorities immediately concerned, knowledge of the trials is restricted to a very small circle and no public statement has so far been made; when it is made, it will therefore require very careful handling.

All the documents discussed above are available for free downloading from the National Archives of Australia among the bundles of files that were submitted to the Royal Commission into Nuclear Tests in Australia in 1985 [A6455,RC 559, Part 3 Item 19052016]. There is no mention in any of them of the 1956 Olympic Games scheduled to open in November 1956.

Despite nearly 500 pages of the File having been submitted to the Australian Royal Commission into British Nuclear Tests in June 1985, the two documents referring to Beale being ‘incorrect’ about the nature of the initiator tests and Home being advised that the ‘true nature’ of the Mosaic were known to the Australian ‘authorities immediately concerned’ were not referred to in the Commission’s Report published in early 1986.

In Volume 1 of the Report the role of light elements as boosts of a fission explosion is discussed (3.1.12-16) but it is concluded that the aspects as explained by the British messages to the Australian Prime Minister and his officials ‘tends to bear out the Eden comment to Menzies that the Mosaic devices were not thermonuclear.’

The official UK historian of the tests, Lorna Arnold, wrote in 1986 ‘The Australian Government took political risks in accepting the trials on Australian territory, but was astonishingly unexacting.’ As indeed was the Royal Commission in the 1980s.

Share and Enjoy !

Subscribe to John Menadue's Newsletter
Subscribe to John Menadue's Newsletter


Thank you for subscribing!