Oscar Wilde insisted that “life imitates art far more than art imitates art”. What would he have made of the present hostage crisis? Twenty-four hours before Iran seized 15 Britons its mission to the UN issued a statement expressing outrage at 300, a movie based on the Battle of Thermopylae in 480BC. In this epic struggle between a small band of Spartans and a massive army of Persians, the ancestors of modern Iran have been painted, the protest ran, as the “embodiment of evil, moral corruption”. They have a point. According to Paul Cartledge, Professor of Greek History at Cambridge University, Persia was “not a one-dimensional barbaric despotism” but, then again, it was “by no means well disposed to Greek-style democracy” either.

Not much seems to have changed in 2,500 years. The behaviour of Tehran over the past ten days has been akin to that of a one-dimensional barbaric despotism, while its contempt for the values of the democratic world is no less acute than it appears to have been in ancient history. Numerous explanations have been offered for this stand-off, including the vagueries of Persian New Year celebrations, long-standing confusion over where the exact boundary in these disputed waters lie and the ambition of the Revolutionary Guard to retrieve some of its men found conducting illegal activities deep inside Iraq. If these explanations are meant to make Iran’s stance seem more credible, then they fail. The real question that should be asked is “Why are we surprised?”.

This seizure is wholly consistent with Iran’s approach to foreign policy for the past three decades. It has been arming and directing Shia fanatics to attack British Forces in southern Iraq for the better part of four years. Its agents in Lebanon, Hezbollah, went into Israel last summer, killing eight troops and capturing two more of whom nothing has been heard since. Its other ally, Hamas, detained another Israeli soldier a little earlier and he too remains imprisoned. All these acts were in strict violation of international standards. Compared with these infamies, obliging soldiers to “confess” to offences that they never committed and publishing supposed letters to the British people must seem minor offences to Iran.

There is endless discussion about how to separate the “moderates” from the “radicals” in Tehran. It is a largely futile exercise. The blunt reality is that Iran has been a menace from the moment that Jimmy Carter, with monumental weakness, decided to force the Shah into exile and so permit Ayatollah Khomeni to return from Paris to assume control. Iran has sought to destabilise the Middle East peace process, undercut Lebanon’s sovereignty and undermine other regimes in the region for almost 30 years. It has done so while men lauded as “moderates” were state president. The Iranian regime has been the embodiment of theological Trotskyism: permanent revolution is the core of its collective ideology. So why are we surprised that it has taken this chance to treat British citizens so badly?

And what has been the response of most of the major powers throughout this period? It has been to express occasional disapproval while building up trade links. Even after the emergence of the firebrand Mahmoud Ahmadinejad it has been business as usual. Over the past five years Iran has moved step by step to be in a position where it can possess nuclear weapons. It has met only limited resistance from a UN Security Council unwilling to do anything more than threaten minor economic sanctions. Iran has concluded, rationally from its perspective, that no one will challenge its attempt to dominate its neighbourhood. The presence of British troops there is an inconvenience. So why are we surprised that it has engineered the opportunity to intimidate them?

What will happen after this incident is over? Iran has every reason to assume that Britain will be more careful about where its forces are stationed. Any place in the vicinity of what could be regarded as Iranian territorial waters may quietly become out of bounds — which means that it will fall under de facto Iranian authority irrespective of cartography. The Iraqi Navy has less muscle than the Swiss one. It cannot impose itself on these awkward straits.

If Tehran calculates that the best way to push the British out of Basra is by turning up the heat, then that is what it will do — or else it might lie low if it concludes that this will hasten our departure. It will then ease into the vacuum. As it does, the smaller Gulf states, especially, will ask themselves whether it may be wiser to appease the Iranian monster rather than oppose its adventurism. So why are we surprised at such aggression against us?

The lasting lessons of this saga should be obvious. They are that Iran in the hands of the mullahs is not, as has been claimed in the past week, “erratic”, “incoherent” or “unpredictable”, but consistent in its outlook and objectives. They are that there will be no stability in the most potentially explosive part of the planet while this regime is permitted to operate as it has been doing. They are that the only plausible middle course between the unattractive choice of backing a military endeavour against Iran or accepting that Iran will have the Bomb is an economic blockade on a scale far larger than France or Germany, never mind Russia and China, have been ready to contemplate. That resolve, though, is essential. For if this is what Iran is already like, what on earth will happen if it ever commands nuclear weapons?

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