According to
Montebello Islands WA: "The first test, which was the first British A-bomb explosion ever and the first A-bomb test to be carried out in Australia, (Emu and Maralinga in SA may be more well known, but they came later), was christened,
Operation Hurricane. This was a 25 kilotonne bomb (Kt, or the equivalent of 25,000 tonnes of TNT) and was detonated on 3rd October 1952 on board the frigate,
HMS Plym, which was anchored off Main Beach on the western side of Trimouille Island. The ship was basically vaporised when the bomb went off. By all accounts a large piece of the ship's boiler can still be seen in the 6-metre deep, 300m long crater that still exists on the ocean floor, while high flying scraps of ship's metal can still be found on nearby Trimouille Island. The second test –
Operation Mosaic G1 – was detonated on the 16th May 1956 and was a 15Kt blast set on a 30-metre high tower at the northern end of Trimouille Island. The final and third test on the islands –
Operation Mosaic G2 – was on the 19th June 1956, which was detonated on Alpha Island. Again it was on a tower and rated as a 98Kt blast; it remains the biggest explosion ever to happen in Australia.
All the islands were closed off to public access from then on, till 1989 when after a safety survey the islands were reopened to pearling and to the occasional visitor."
