These Aussie islands were a secret test site for A-bombs. Now you can visit

In the 1950s, unbeknown to the Australian public, the British government tested three atomic bombs in the Montebello Islands off the Pilbara coast. The last was five times larger than the atomic bomb that flattened Nagasaki.

The Montebello Islands from above – the site of 1950s bomb tests.

Boom. Then for 70 years after, nothing but secretive silence and understated signs (“Elevated radiation levels exist here”) to warn visitors away. But anyone with a sense of adventure can visit – at least for a while.

The Montebellos are hard to get to: their remoteness is what attracted the British bomb testers. They appear like pie crusts on the horizon as I squint from the deck of my small Coral Expeditions cruise ship.

Alpha Island is low and grey-green and as we putter into Burgundy Bay on our tender, stingrays drift below in the blue and purple water on this sunny day.

Anywhere else we’d be getting out our picnic or fishing rod, splashing in the warm fish-flitted water, and perhaps overnighting in one of the beautiful inlets nibbled out of low-lying cliffs.

Not here though. As we scramble ashore, we’re confronted with a stark wooden board warning of the island’s dark past and dangers: “Avoid causing dust as any particle may be radioactive. Do not handle or remove objects.”

Remnants of bomb-testing buildings at Timouille Island.

You should only stay an hour, the sign says. Then get going before you grow an extra head or start glowing.

Okay, the sign doesn’t actually say that, but it implies it. It’s our Coral Expeditions team that makes those jokes, although these islands are deadly serious. Our accompanying geologist Ian Herford loves rocks, but here he won’t even pick them up for a closer look.

Don’t touch, don’t linger. There are no fishing boats here, or pleasure craft, or campers. No Indigenous people. Our ship Coral Geographer hovers offshore. Our tender slips in and, an hour later as anxiety levels rise, we’re chugging away again.

Trimouille Island, one of two islands the British government secretly tested atomic bombs on.

Why would you visit the Montebello Islands? Well, an expedition cruise along the Coral Coast and up to Broome is a wonder of islands and superb reefs mixed with adventure and quirky history, and the Montebellos are one of Australia’s most curious corners, forever associated with the mid-20th-century paranoia of the Cold War.

The British tested atomic weapons on Alpha and Trimouille islands in a secret personal agreement between the British and Australian prime ministers. The first in 1952 saw Britain become the world’s third nuclear power after the US and the USSR.

The British never shared all their data, nor kept their promise on the size of the blasts. The last Montebello explosion in 1956 was officially 60 kilotons but it was later admitted that it was nearly 100. The fallout contaminated most of northern Australia, and radiation was detected as far away as New Zealand.

An obelisk marks ground zero on Alpha Island where the third bomb was set off. It sits in the middle of a sunken crater scattered with rock rubble now prettily overgrown with creepers sporting festive purple flowers.

Rusty rails lead up a hillside to a concrete platform where the pillbox for observation was improbably located, only a few hundred metres from the blast site. A concrete platform remains, and scraps of twisted metal that nobody dares touch.

It’s beating hot as we return to the bay. The surf sucks on a beach gritty with white seashells. Oystercatchers strut on orange legs. The forbidden water is tourist-brochure blue and seems inviting. But we aren’t fooled. We hoist anchor, and scurry away from one of Australia’s strangest places.

THE DETAILS

Coral Expeditions’ 12-night “Abrolhos Islands and the Coral Coast” itinerary between Fremantle and Broome (or the reverse) visits the Montebello Islands and other destinations including Ningaloo Reef, the Dampier Archipelago, Shark Bay and the Abrolhos Islands. The next departures are February 20, March 2 and 23 and September 22, 2024. From $9570 a person twin share.

A 12-night “Ningaloo & Bluewater Wonders” expedition return from Broome also visits the Montebello Islands with departures on September16, 2024. From $10,700 a person twin share. See coralexpeditions.com

The writer travelled as a guest of Coral Expeditions.