President Ahmadinejad was determined to milk as much publicity as possible from Iran’s decision to release the 15 British sailors and Marines held captive for 13 days. In a stage-managed press conference, he spent more than an hour denouncing Western policy in the Middle East, justifying Iran’s actions and blaming the Royal Navy for trespassing in Iranian waters before his theatrical announcement that theHMS Cornwall crew were being freed as a “gift” to the British people. In doing so, he showed considerable flair in deflecting attention from Iran’s isolation, glossing over the split within the Tehran Government and highlighting an eccentricity that is a wonder to behold.

Downing Street gave a warm and simple welcome to the group’s release. It wisely chose not to rebut any of Iran’s nonsense and exaggerations or to make political capital out of a denouement that was as important to the Government as it was appreciated by the captives’ families. So what are the lessons of a crisis that was caused by Tehran and was as much about internal Iranian politics as foreign policy?

The first is that in dealing with a maverick and unpredictable country such as Iran the West cannot rely on past experience. Tony Blair hoped at first that quiet diplomacy would lead to the swift, face-saving formula that secured the release of British servicemen seized in a similar incident three years ago. But after four days it was clear that this was achieving nothing except to make the Government look weak abroad and spineless at home. It was important to demonstrate to Tehran that the political costs would rise sharply, and Mr Blair was right to make clear the consequences. He was also right to push for a strong statement of condemnation by the UN Security Council and to invoke the support of Britain’s European partners. Both underlined Iran’s isolation without threatening consequences that might have prompted pragmatists in Tehran feel compelled to support the Revolutionary Guards.

Determining the degree of public pressure is especially difficult if a government does not know who is controlling events or which faction is predominant in Tehran. But Britain probably got it right. It was also significant that other Middle East governments offered support to Britain, and that the Vatican used its good offices.

Several things must now follow. There should be no recriminations over the broadcasts and “confessions” made by the captives. It was patently clear that they acted under huge duress — and until a detailed debriefing, their actions must neither be judged nor condemned. What they do say, however, must be central to an analysis of military policy in the Gulf. Are the patrols of the disputed waterway safe, necessary and properly co-ordinated? Are the terms of engagement for British frigates and Marines appropriate? Should Britain now press for a proper and universally accepted delineation of international frontiers in these shallow waters?

It is difficult to conclude that Iran’s actions were other than premeditated. The incident underlines the pride and prickliness in Tehran, the sense of encirclement and the willingness to make ruthless use of Iranian influence in Iraq to thwart the West, especially over Iran’s nuclear policy. Tehran has, however, been forced to climb down. The enduring lesson is that Iran remains highly unpredictable, an enigmatic mixture of fanaticism and pragmatism, and that the greatest victims are the people of Iran.