Keir Starmer’s giveaway of the strategically important Chagos Islands to Mauritius is an outrageous act of folly which relegates the British national interest and puts anti-patriotic, left-wing ideology centre stage.

Not only have we handed the entire Chagos archipelago in the Indian Ocean to a long-term ally of China, but the British taxpayer has also been signed up to pay for the privilege, with a special new UK fund being set up bankroll those whose families were originally from the islands to visit or resettle them.

The arrangement opens up the possibility of China compromising the viability of the joint UK-US military base on the biggest of the islands, Diego Garcia. Over decades to come there is little to stop the Chinese setting up a surveillance centre or even their own rival base on a neighbouring island. While the US has welcomed the deal on the record, it has emerged that behind the scenes it had told Britain of its opposition to ceding sovereignty. There was no necessity for us to do so, especially given that Mauritius is well over 1,000 miles from the Chagos archipelago which was never part of its own sovereign territory going all the way back to when it became an independent nation itself.

The deal advertises not only the general weakness of Britain under Starmer, but also the lack of political will of his administration to defend British territory the world over. Already, Spain is redoubling its claims over Gibraltar, while Argentina has issued a new declaration about its determination to get sovereignty over the Falkland Islands.

Argentine foreign minister Diana Mondino said: “We welcome this step in the right direction…we will recover full sovereignty over our Malvinas Islands.” While this is unlikely to involve a new military assault for the foreseeable future, it almost certainly will involve enlisting the support of anti-British international legal bodies, just as Mauritius did in the Chagos Islands dispute.

Instead of ignoring the opinion of the International Court of Justice – which is supposed to be just an advisory body in territorial disputes – that Britain should give up Chagos sovereignty, Starmer has demonstrated that he will generally elevate the nebulous notion of “international law” above the national interest. As a former colonial power, we can now expect the world’s developing countries to gang up against us in all manner of international tribunals.

Would Starmer have put together a military taskforce to recover the Falklands after the 1982 Argentine invasion? Just to ask the question is to know the answer. At best, he would have settled for the idea – pushed by chinless wonders in the Foreign Office at the time – of “joint sovereignty”. And that would have put British subjects in the Falklands on a one-way ratchet towards permanent Argentine rule.

The faith of Starmer and Foreign Secretary David Lammy in the fiction of a so-called “rules-based international order” will make them a laughing stock the world over. The reality, encapsulated by the word “realpolitik” – originally a German term, funnily enough – is that it is a combination of economic and military strength that secures territory, not the windy declarations of international lawyers. Yet Labour has just scrapped a commitment to raise the share of GDP spent on defence.

So prepare for an onslaught of new overseas legal claims against Britain – for “reparations” over the slave trade that this country actually did so much to end, or over our supposed guilt in being the first nation to industrialise and therefore to start emitting greenhouse gases. Never mind that doing so led to life-enhancing technologies coming on stream for the whole world.

Starmer’s mentality of surrender fits a long-established pattern of the British political class allowing its country to be mugged by others, going back to Tony Blair giving away half our hard-won annual EU rebate in return for ill-defined reforms of the Common Agricultural Policy which were never delivered. Or Theresa May letting Brussels dictate which issues should be settled first in the Brexit negotiations – surprise surprise, it was their shopping list of priorities that got agreed and then they began playing hardball over ours. Or indeed the bloated foreign aid budget that hands billions to corrupt regimes that seldom do us any favours and won’t even take back their citizens who have entered Britain illegally.

It was Margaret Thatcher who won that UK rebate from Brussels, won back the Falklands and helped the West win the Cold War by being resolute about defence. How we could do with similarly strong and unabashed leadership in the national interest right now. We have already seen that we are not going to get it from Starmer.