The Operation Totem tests of 1953 had been carried out at Emu Field in South Australia , but it was considered unsuitable . A new , permanent test site was being prepared at Maralinga in South Australia , but would not be ready until September 1956 . It was therefore decided that the best option was to return to the Monte Bello Islands , where Operation Hurricane had been conducted in 1952 . A 15 July deadline was set as the terminal date for Operation Mosaic to allow the task force flagship , the tank landing ship , to return to the UK and refit for Operation Grapple , the planned first test of a British hydrogen bomb . The British government was anxious that Grapple should take place before a proposed moratorium on nuclear testing came into effect . The second test was therefore conducted under time pressure . At the time of the Royal Commission into British nuclear tests in Australia in 1984 – 1985 there emerged a claim that the second test was of a significantly higher yield than suggested by available figures : as compared to ; but this claim remains unsubstantiated
Operation Hurricane
Operation Hurricane
Operation Mosaic