Captain Christopher Smith has measured out a running route. If he jogs 25 laps of the flight deck he clocks up 10km. If it’s not too windy he might do some sprints up the so-called “ski jump” (more on this in a moment) of HMAS Canberra, the new flagship of the Royal Australian Navy. Otherwise this curved ramp at the end of the flight deck is useless, perhaps the only part of this pristine 27,000-tonne vessel that has no specific purpose.

Commissioned in November 2014, Canberra is a behemoth by the standards of the modern Royal Australian Navy, bigger even than its last aircraft carrier, HMAS Melbourne, which was sold for scrap in 1982. Canberra might look like an aircraft carrier but it’s not: it’s an amphibious assault ship designed to transport and deploy troops and helicopters to seize a beachhead or port.

It’s a major step up in capability for Australia and a sign of the country’s status as a middle power. And Canberra is not alone. It has an identical sister vessel, HMAS Adelaide, that was commissioned in December 2015. Each of the vessels – called Landing Helicopter Docks (LHDS) by the Australian navy – is 230 metres long, boasts a 21-chef galley that can produce 4,000 meals a day, has accommodation for 1,400 personnel and room for four amphibious landing craft that can each shift 170 troops at a time. Both can each carry 110 armoured vehicles and fit eight MRH-90 helicopters in the hangar, with room for more on the flight deck.

These ships can each supply enough power for a city the size of Darwin and produce fresh water from the ocean. But an LHD is not just its own floating township: it can also sit off the coast and support a city that has been hit by a natural disaster. It can land troops where there is no port or where the port has been destroyed by a tsunami.

“When I joined the navy as a country boy at 19 I never thought I’d end up here,” says Cpt Smith, 46, who hails from western New South Wales. “I grew up in a town with less than 1,000 people and no water for miles. Now I’m running a ship with a population up to 1,400, surrounded by water.”

Canberra’s operations rooms are packed with the latest technology and the two LHDs can combine to form a powerful command and control network. Together, says Cpt Smith, they could run “a sizeable chunk of the Australian army, navy and airforce”. Their arrival, he says, marks a shift to a higher level of co-operation between the services.

In short the twin vessels are bursting with capability, which makes the superfluous “ski jump” even more of an intriguing anomaly. It was part of the design by shipbuilding firm Navantia, which built it into the Spanish vessel, Juan Carlos 1, to launch fighter jets. So it is not, in fact, entirely useless but it serves a purpose that Australia says it does not want.

When then defence minister Brendan Nelson awarded Navantia the AU$3bn (€1.9bn) contract to build two LHDs for Australia in 2007, he considered having the ski jump removed to avoid the suggestion that the vessels might ever be converted to aircraft carriers. “I was advised removing it would cost AU$35m [€23m] per ship,” says Nelson, who is now director of the Australian War Memorial. So the ramp stayed. Still, the idea that these amphibious ships could become aircraft carriers or even be adapted to launch jump-jet F-35B joint strike fighters surfaces every now and then. Former prime minister Tony Abbott was keen on the idea and was reported to have demanded a study into such an option. The plan was quietly killed off before Abbott was ousted as leader last September.

Nelson still vehemently opposes the aircraft carrier idea. “Australia cannot and should not responsibly consider that,” he says. “We don’t need it.” And Cpt Smith, Canberra’s commanding officer, agrees. “If you turn this into an aircraft carrier you lose the ability to do amphibious operations,” he says. “To put joint strike fighters on it would be an enormous change in message to the region.” Were the LHDs to have greater reach and offensive air strike capability, Australia’s neighbours may question why it was needed and where it would be targeted.

Instead, Canberra and Adelaide are said to have a purpose that is much more marketable in the region and suggests a more friendly military. “In the immediate future the ship is going to be operating in humanitarian assistance and disaster relief and non-combatant evacuation operations, and providing support to regional neighbours in a range of crises,” says Cpt Smith, adding that it is most likely to be deployed in Southeast Asia and the Pacific or responding to natural disasters on Australia’s coastline. The navy has held talks with non-government organisations such as Red Cross, Red Crescent and Doctors Without Borders as to how the ship could support their crisis-response work.

But for all the emphasis on its humanitarian abilities, the LHD is still a warship. This is underlined when Able Seaman Ayesha Sweeney, a medic, shows us around Canberra’s hospital facilities. There’s a pathology laboratory, two operating theatres, an intensive care unit for eight patients and 40 beds. It’s a reminder that this ship is built for combat and the possibility of casualties which that entails.

“I certainly hope that over the 40 years we have the LHDs they are never used for amphibious assault,” says Nelson. “But at least we have the capability to do that if we’re required to do so as part of a multinational force.”

These vessels had their genesis in what feels like another era. It was around the turn of the millennium and the Australian Defence Force (ADF) had just staged its biggest military deployment in decades, in Timor-Leste. The Australian-led intervention was a success but it was a challenge for the navy to transport and maintain supplies to some 5,500 troops. “In fact, if it hadn’t been for a civilian ferry they had on lease at the time they would have really struggled to do it,” says Andrew Davies, director of the Australian Strategic Policy Institute’s Defence and Strategy Program.

The HMAS Manoora and Kanimbla, two relatively small amphibious vessels bought second-hand from the US Marines in the late 1990s, were nearing the end of their lifespan. The Australian government, at that stage flush with cash, had to make a decision about replacing the ships. Around this time, then prime minister John Howard outlined a new foreign policy doctrine. In an interview with now defunct magazine The Bulletin, Howard described a new role for Australia in the Pacific, supporting the global peacekeeping efforts of the US. In a phrase that would come to haunt Howard and cause tensions with neighbouring countries, the magazine said Australia aspired to be the region’s “Deputy Sheriff”.

To do this the ADF had to boost its ability to move troops and equipment around the region. The argument as to whether Australia needed amphibious assault capability was never had but at the time the government could afford it. “It was a perfect storm of money and the recognition that we needed extra capacity,” says Davies. “And if you need sea lift capacity and you’ve got the money, you might as well go with amphibious capability as it gives you more operational flexibility.”

For Hugh White (see page 54) who was at that time working in the Australian Defence Department, it was “a terrible and heroic waste of money”. He argued for the purchase of a fleet of five ships that would have been only marginally larger than the ones they were replacing. Instead the government opted to fork out on two mega-ships that were three times the size.

“There has never been a clear reason as to why Australia decided to buy the LHDs, to buy an amphibious assault capability, and there never could be,” says White. “Big amphibious ships like that are big, fat sitting-targets. If there’s a crisis in the South China Sea, we won’t send the LHDs because the navy knows the LHDs would be enormously vulnerable.”

White acknowledges that the ships will be fine for stabilisation operations in the Pacific but says smaller vessels could have done this. And having more of them would have ensured one was always available. Davies can see a purpose for them but concedes the LHDs might not have been first choice in these straitened times. “Imagine law and order blows up in Papua New Guinea and the government needs to do a service-protected evacuation,” he says. “The ability to land lots of people via helicopters and perhaps seize a port or airfield or establish order in major arterial roads, I think, is a really valuable thing to have.”

Cpt Smith’s pride is obvious but it is when we get down into the bowels of Canberra, to the amphibious landing dock, that he declares we have reached “the coolest part of the ship”. There’s a massive armoury down here but it’s also where the four 2,000-horsepower landing craft, each capable of carrying an M1A1 Abrams tank, shunt back and forth when the ship is in amphibious landing mode. When Canberra was put through its paces during exercises off Townsville in 2015 the craft conducted more than 440 beach landings. One scenario saw the ship and its troops evacuate role-playing civilians from the beach, bring them on board via the landing dock and provide medical attention to those needing it.

The next challenge will be when Canberra attends Rimpac (the Rim of the Pacific Exercise), the world’s largest international maritime exercise, near Hawaii in June and July. Having tested its capabilities the navy is keen to show them off. And it’s not just the navy: the army is training a battalion with amphibious skills to work on the LHDs. They are training in Townsville, where Canberra expects to spend a lot of time. In its first year the focus has been on integrating its 400-strong crew and the army contingent that will work with it. The LHDs are scheduled to be declared a fully operational amphibious capability by mid-2017.

Nelson is adamant that the LHDs were a good investment; he sees it as hoping for the best, preparing for the worst. “I won’t be alive in 40 years but I will be very pleased if in 40 years someone says ‘That was a waste of money because we never used them,’” says the former defence minister. “We can only pray.”

That’s probably not the prayer being offered up by Cpt Smith and his ship’s company. No doubt they are keen to use Canberra’s extensive capabilities in a real-life situation. Everything, that is, except the ski jump.