Australia has told Britain that, if it wants to get a free trade deal after leaving the European Union, it will be expected to offer Australian citizens the same immigration rights that European citizens will enjoy in Britain.
In a move which underlines the historical complexities and practical difficulties Britain faces in striking new trade deals, Ms Julie Bishop, Australia's Foreign Minister, has now publicly told London that her country will be "disappointed and concerned" if Britain continues to discriminate against Australian citizens in granting work permits.
And Mr Alexander Downer, Australia's top diplomat in London, turned the political pressure even higher, by telling the local media that Canada and New Zealand are also demanding freer visa regimes.
Until the early 1970s, there were few immigration controls between Britain, the old colonial master, and Australia, Canada and New Zealand, a group euphemistically referred to at that time as "the dominions", since they all retained - and continue to retain to this day - the British monarch as their head of state.
In theory, this had nothing to do with shared race or skin colour. In practice, it was all about that; a mere generation ago, officials in London still talked about the "White Commonwealth".
And the links were close. For most young Australians or New Zealanders, going to Britain to work temporarily in what were often menial jobs was regarded as a rite of passage; the western London area of Earl's Court was commonly known as "Kangaroo Court" as it was largely populated by Australians.
For many Britons, immigration to Australia and New Zealand was the easiest lifestyle choice, since these two countries offered cash to ease the passage. More than a million Britons migrated under such schemes which operated until the 1980s; they went down in history as the "Ten Pound Poms" after the subsidised travel fare they were charged and the nickname for people of British descent. They included the families of two recent Australian prime ministers: Julia Gillard and Tony Abbott.
All this changed when Britain joined the European Union, and had to offer free entry and work opportunities to EU citizens, while imposing a common visa regime on those outside Europe. And, in a pattern repeated with other former colonies, Britain, which used to buy most of the Australian and New Zealander agricultural output, simply dumped its partners.
The politicians in power in London today show no sign of recalling any of this history. Soon after the British voted to leave the EU in a referendum last year, they rushed to Australia to propose free trade deals, on account of the countries' shared history.
Australians responded positively: "As Britain moves to completing its exit from the EU, we stand ready to enter into a free trade agreement with the UK as soon as the UK is able to do so", said Australian Prime Minister Malcolm Turnbull during a visit to London last month, to the evident delight of his British counterpart Theresa May.
But the Australians point out that since Britain is leaving the EU, there is no reason Australian citizens should now be treated any differently from Europeans in a future British immigration regime - if Europeans will continue to have an easy time crossing Britain's borders, so should Australians.
London is confronted with a painful dilemma. For, in its effort to preserve extensive trade links with Europe, it is touting the possibility of maintaining preferential immigration treatment for European citizens.
In theory, such a preferential deal could also be extended to Australians or Canadians. But it will be difficult to explain why only a handful of predominantly white former British colonies should benefit, and not a country like India, whose citizens need a tourist visa even for visiting. Yet loosening immigration controls for India will be tantamount to electoral suicide for Mrs May. Predictably, British officials now prefer to avoid any discussion on this topic, although they admit that the issue cannot be kept hidden from debate for long.