As mayor of the city, the former Revolutionary Guard commander Mahmoud Ahmadinejad, 49, felt the footballer’s face was at odds with his conservative vision for the capital. Beckham, the first foreigner to be used in advertising in Iran since the 1979 revolution, was pulled from sight. If Mr Ahmadinejad, the nightmare option for Iran’s reformists and the West, wins on Friday, Iran’s international relations seem certain to take a similar plunge.

Mr Ahmadinejad, notoriously hostile to the US, said during his campaign: “America was free to sever its ties with Iran, but it remains Iran’s decision (whether) to re-establish relations with America.”

His victory surprised Iranians and foreign observers alike. Yet at the last minute the regime decided to throw its weight behind the slightly built conservative, mobilising its network of Basiji, the loyalist volunteer force, to vote en masse for him.

His simple message of populist economics and social concern also attracted Iran’s poor, allowing Mr Ahmadinejad to sweep from nowhere into second place with 19.5 per cent of the vote — less than 2 per cent behind the favourite, Hojatoleslam Ali Akbar Hashemi Rafsanjani, whom he now faces in the second round.

Ebrahim Yazdi, the leading figure in the Freedom Movement for Iran, a pro-reform organisation, said: “It’s a military coup through an election process.

“The Basiji are not supposed to get involved, but their facilities were used to vote for Ahmadadinejad, and they have an office in every village in Iran.”

Though the 12-man Guardian Council yesterday verified the result of Friday’s vote, they gave defeated candidates three days to submit allegations of fraud. Mehdi Karroubi, a reformist candidate who came third, has already accused the Basiji of voter intimidation and illegally controlling some polling stations.

Yet the shock result seems more the product of Iran’s opaque politics than widespread fraud.

An entrenched believer in Iran’s right to a nuclear energy programme, Mr Ahmadinejad will be a hard man with which to negotiate for the West. A civil engineering graduate, he was born in a poor quarter of south Tehran and was a student revolutionary during the 1979 overthrow of the Shah. At the start of the war with Iraq he joined the Revolutionary Guard and went on to become a special forces commander, operating behind enemy lines. He became Mayor of Tehran in 2003, a tenure marked by the curtailing of reform and a return to Islamic cultural discipline. “We did not have a revolution in order to have democracy,” Mr Ahmadinejad once said. Paradoxically, President Bush contributed to his ascent with an eve-of-election statement in which he said that the Iranian constitution was undemocratic. The regime spun the message brilliantly, telling Iranians that Mr Bush was ordering a boycott: the public voted in droves as a reaction, giving a 63 per cent turnout that exceeded the most optimistic expectations.

Ghasim, a 42-year-old Ahmadinejad supporter in south Tehran, said: “I wasn’t thinking of voting until Bush encouraged us not to. It was like an interfering neighbour affecting family decisions. When I heard he wanted a boycott, I went out and voted immediately.” About 37 per cent of the electorate chose not to vote, however, and those people — likely to be disillusioned reformists — are expected to swing behind Hojatoleslam Rafsanjani in the second round.

The conservatives can historically count on between 15 and 20 per cent of the vote, so Mr Ahmadinejad’s mandate ought to be placed in context: he is still unlikely to be Iran’s President.

But nowhere is the fear that he may win heavier than in the hearts of Tehran’s liberals.

“Hold your nose and rally behind Rafsanjani,” urged Sharq, Tehran’s reformist newspaper, persuading its readers to take a step they would not have dreamed of only two days ago.

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