The Iranian regime may have won a boost at home from the melodrama it has scripted over the past fortnight, but it is likely to pay a price abroad, even from its usual allies.

Relieved British officials, who were puzzling yesterday over which diplomatic moves had done the trick, had most confidence in the rallying of international support. “Our contention is that they were brought to this position [releasing the crew] by international pressure, which convinced them the game was not worth a candle,” said one senior British official.

“Afghanistan, Syria, Iraq, the Saudis were all active — even Colombia called in its Iranian Ambassador,” he added. Iranian officials “were finding, as they got back from [their new year] holiday, that their phones were ringing off the hook saying that they were in the wrong place”.

Syria, as “Iran’s closest friend in the region”, may have been particularly important, officials believe, and Britain had encouraged it to be a go-between. “To have the Syrians going to Tehran and saying that this is not a good idea is indicative” of the deep discomfort in the Arab world, said one. The controversial British policy of making overtures to Syria, in the face of the Bush Administration’s refusal to have contact, may have reaped at least this reward.

The display of the unpredictable and confrontational nature of the Iranian regime may also help Britain and the US to win solid support for tougher sanctions if Iran refuses to curb its nuclear programme. The seizure of the crew coincided with a second UN Security Council resolution, taking a step farther up the scale of financial curbs and travel bans.

The past fortnight has “opened up new channels” that may make it easier to explore Iran’s flexibility on the nuclear front, in the six weeks before the resolution’s deadline expires. Iran’s leaders, who displayed confusion over the British crew, have so far been consistent in refusing to freeze uranium enrichment, the most contentious work. But one British official has suggested that the release of the crew was an encouraging sign that Iran likes to preserve a claim to international legitimacy for its actions.

British officials are more puzzled about the chemistry of their direct dialogue with Iran. For days, they found it hard to get hold of Ali Larijani, Iran’s chief international negotiator, even though he was an obviously desirable contact; in the nuclear talks, he has proved pragmatic and moderate, at least by the standards of this regime.

When Larijani appeared on Channel 4 News at the start of the week, and later spoke on the telephone to Sir Nigel Sheinwald, the Prime Minister’s adviser, “it was clear to us it was moving towards a diplomatic solution”. Asked why Britain simply could not get hold of him, one official said: “He wasn’t taking calls — that perhaps reflects that they didn’t have a coherent position.” Another added: “If Iranians don’t have an answer, they don’t answer the phone.”

Britain has denied that any bargain was struck for the crew’s release. British officials were surprised by the US and Iraqi release of a detained Iranian diplomat, and dismissed Iranian claims that Britain had apologised. “There has been no apology — they need to look at their translation,” one said.

Asked whether he admired President Ahmadinejad’s presentation of the release as an Easter “gift”, one senior official said: “I don’t do admiration. I’ve been in this job too long.” But if he admitted to a flicker of that sentiment, he said, it would be for Ahmadinejad’s inclusion of the Jewish celebration of Passover in the list of reasons for the release. He offered, with what counts for effusiveness in the British Civil Service, that “that was quite good”.

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