As Britain’s dispute with Iran waxed and waned over the past 13 days, ministers and officials in London tried to avoid one word: “hostage”.

President George W. Bush twice used the term to refer to Iran’s detention of the 15 British sailors and marines, stirring memories of the 1979-1981 US hostage crisis in Tehran. But this was a parallel that London desperately did not want to make.

“This is not a hostage crisis,” Sir Richard Dalton, former British ambassador to Tehran, said yesterday, shortly before the captives were released. “Iran is not using their capture to achieve specific benefits.”

At the back of British diplomats’ minds lurked the fear that the dispute would drag on as the US hostage crisis had, leaving Britain looking all but impotent. It was not the kind of legacy that Tony Blair – expected to announce his resignation as prime minister in the next few weeks – wanted.

For much of the period, British diplomats were confused: uncertain of who was taking the decisions in Iran, unable to establish useful lines of communication and unclear what Iran really wanted.

Frustration with the lack of Iranian response lay behind one of the UK’s most controversial decisions during the dispute: making a public presentation last week of its case that the detainees were in Iraqi rather than Iranian waters.

British officials did so knowing that Iran was likely to respond as it did – by screening “confessions” from the prisoners. London also angered Tehran by going to the United Nations, although the two sides subsequently sought to reduce tensions by an exchange of diplomatic notes and a statement on Saturday by Margaret Beckett, the UK’s foreign secretary, that “everyone regrets this position has arisen”.

But as soon as Iran’s ruling elite prepared to return from their new year holiday on Monday, Ali Larijani, the senior security official and chief international negotiator, chose an interview with Britain’s Channel 4 news to broadcast a conciliatory message, emphasising the desirability of a diplomatic solution.

Britain was still waiting for a more formal contact from Tehran and, on Tuesday evening, Ms Beckett expressed caution against hopes of a rapid diplomatic breakthrough.

Hours later, Mr Larijani made the most significant diplomatic contact of the entire crisis. He called Sir Nigel Sheinwald, Mr Blair’s top foreign policy adviser, and told him the UK could best help resolve the dispute by calming things down.

Downing Street immediately issued a positive press statement, highlighting the desire of “both sides” to find a solution. From then on, British officials’ confidence grew that the captives would be released, even though they were taken aback by the speed of events.

Seeking to allay criticism over the UK’s shift of pace, British officials argue that the combination of pressure and diplomacy paid off where a purely “softly softly” approach would have failed.

British officials also reject any linkage between the 15 UK navy personnel and the fate of five Iranian detainees held by the US in Iraq or the release this week of Jalal Sharafi, an Iranian diplomat kidnapped in Baghdad.

However, although neither Mr Larijani nor any of the other Iranian interlocutors brought up the subject of the Iranian detainees, Britain has praised the role of Iraq in helping to resolve the dispute. Iraq has campaigned for the release of all six Iranians.