THE reopening of Britain’s embassy in Tehran is, like the recent P5+1 nuclear power agreement, a positive development.

Both will help ease tensions between the Iranian regime and the major imperialist powers, notably the US and Britain.

Importantly, too, such moves towards normalisation should herald the end of Western sanctions against Iran. Ostensibly, these were aimed at the Islamist regime, although their real intention was to hit the ordinary people of the country in the hope they would rise up against an oppressive theocracy.

But it would be unwise to mistake the Iranian thaw for a progressive turn, either in the foreign and domestic policies of Iran’s rulers or in British foreign policy in the Middle East.

Iranian ruling circles from Supreme Leader Ali Khameini and President Hassan Rouhani downwards recognise the threat posed to their fellow Shi’ite Muslims (and therefore their real or potential allies) in Iraq, Lebanon, Yemen, Kuwait and Bahrain by Sunni Muslim fundamentalism, spearheaded by Isis and al-Qaida.

They understand what too many Western politicians still fail or refuse to see, that behind this vile sectarianism lies the malign machinations of the Saudi Arabian and allied Wahhabist dictatorships.

Although the Shi’te population in Syria is relatively small, the Tehran regime also appreciates the strategic position occupied by the Assad government in Damascus, which is fighting to protect all ethnic and religious minorities against a murderous Isis assault backed by Sunni powers and helped by Nato support for anti-Assad insurgents.

Syria also presents a massive barrier to Isis penetration into Lebanon, hence the deployment of the Iranian-backed Lebanese Hezbollah militia in the war against Isis.

This complex kaleidoscope highlights the utter bankruptcy of US and British policy in the region, characterised as it is by duplicitous scheming in the interests of Western big business.

Barack Obama and David Cameron proclaim the overriding need to roll back and destroy Isis — yet they plot with Turkey to carve up and occupy Syria, while President Recep Erdogan’s airforce bombs the bases of Kurdish guerillas who have done more than anyone else to take on the Isis barbarians in Iraq and Syria.

At the same time, the Saudi Arabian airforce, equipped and trained by Britain and other Nato powers, remorselessly lays waste to Yemen to shore up its preferred politicians, trying to wipe out the Houthi movement which stands in the front line against al-Qaida and Isis in that country.

So why the seemingly contradictory rapprochement with Iran?

Anti-Isis considerations may be a factor. A message is being sent to Saudi Arabia — and perhaps even to the most intransigent elements in Israel — that the West has a choice of more than one or two horses to back in the Middle East. It is thus a matter of realpolitik to work with the Iranian regime, as well as against it.

But above all, in the case of the British ruling class, better relations with the world’s third-biggest oil exporting nation is a case of doing lucrative business.

The little publicised fact that Foreign Secretary Philip Hammond took a coterie of top oil, banking and other business executives with him when reopening the British embassy demonstrates the truth of Lord Palmerston’s maxim: “We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual.”

The real interests of the people of Britain and Iran — best served by a socially just Middle East free from imperialist interference — are something else entirely.