The US and Britain are so worried about our security, and so keen for our help in restraining China, that they are allowing us to see secrets that for more than 60 years they have shared only with each other.

The agreement under which Washington and London will support us in building a fleet of nuclear submarines, announced on Thursday, has further implications for our defence: it means we'll get access to more technology that was formerly off limits to us.

Our elevated status has been formalised with the creation of the AUKUS security partnership, in which Australia, the UK and US will deepen their sharing of know-how, and increasingly integrate their military science, technology and industrial bases.

That sounds like we're really being knitted into a three-country technology and manufacturing complex.

Our relaunched submarine program, replacing the former effort to build big diesel submarines with a French partner, still does nothing for our short-term security, however. Indeed, delivery of the first nuclear boats will reportedly come a few years later than the 2032-33 date expected for the diesels.

That's bad. Really bad.

On the other hand, with this move we're really showing the US that we're serious. Uncle Sam is inclined to help those who help themselves.

What a contrast there is between this momentous business and the inane reaction in Wellington to our attempts at improving our security and, incidentally, New Zealand's. Our nuclear submarines will be banned from New Zealand waters, says Jacinda Adern. Thanks.

Since the name became public a few years ago, there's been great awareness of the decades-old Five Eyes intelligence partnership between Australia, Britain, Canada, New Zealand and the US. But within the alliance there has always been a walled-off area to which only Britain and the US have had access.

Beyond that wall, those two share especially sensitive technology. This includes not just nuclear secrets but also the most crucial information about submarine design. This co-operation between them began in the 1950s.

Now our engineers and naval personnel will learn about the technology of US and British naval reactors and such things as how to make nuclear submarines extremely quiet and thereby hard to detect.

Relentless Chinese aggression, and especially the risk that Beijing could threaten Australia at short range after achieving dominance over south-east Asia, is one reason for this development. Our allies are obviously worried about us.

Another is that Australian military capability helps to deter China. The US needs strong allies on this side of the world. It will be thinking especially about the risk of a war over Taiwan, though we have no commitment to help Washington defend the island.

If the US will let us have its submarine secrets, we can hope for access to more of its advanced technology, such as new types of ballistic missiles and sophisticated sensors. Australia will also contribute to more US development projects now that it is allowed into them.

Chinese military technology is advancing rapidly. It's essential for us to try to stay ahead, which will become much easier if the Americans let us have some systems that they previously kept for themselves (and the British).

The government said last year that defence planning could no longer assume this country would not be attacked within 10 years. So we're not safe in the 2020s. But our military acquisition plan is full of programs that will do almost nothing for our security before the 2030s.

Now delivery of the first replacement boat for our six Collins-class diesel submarines is not expected until after 2035. We could be under great strategic stress well before then, so some compensating enlargement of capability needs to be added to defence planning.

Even the first of the new submarines will be built in Adelaide, whereas the fastest possible program might have left that one, and maybe the second, in the hands of the foreign builder that will be the designer.

At least no one is talking about making heavy modifications to a foreign design. There are two available: the US Virginia class and British Astute class.

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Since Prime Minister Boris Johnson says British companies will be involved in this program, there's a good chance that what we'll get will be a modified version of the Astute, perhaps with a US system for controlling weapons and sensors.

The seven Astute-class boats in service or under construction for the Royal Navy are magnificent submarines, displacing 7000 tonnes when surfaced and carrying an unusually large number of torpedoes and missiles.

We must hope that, if our new subs will in fact be Astutes, British builder BAE Systems and propulsion supplier Rolls-Royce can quickly begin making major parts of the first boat in their facilities - regardless of the made-in-Adelaide commitment.

Then they would gradually transfer work to the unprepared Australians.

In that respect, a challenge is that the British companies are already heavily loaded with not just the Astute program but construction of the Royal Navy's new Dreadnought-class ballistic-missile submarines (enormous nuclear-doomsday weapons).

The three countries will spend 18 months working out exactly what Australia should buy. Temptations to add design complications that will delay delivery must be avoided.

In their early years of service, these submarines will have to have many British and American crew members, because we just do not know how to operate a nuclear propulsion plant. Australian sailors will gradually learn how to do it, but this point alone highlights just how deeply intertwined we are becoming with our two main defence partners.