There had been an accident on Valiasr Street, one of Tehran’s main thoroughfares. The two drivers, along with two passengers from one of the cars, had been taken to hospital with minor injuries. One of the passengers was Hassan Jabari, a high-ranking jurist and politician. The other passenger’s identity was unknown, but a bystander had filmed the aftermath of the accident on their phone and a still from that movie was embedded in the message.

Martin squinted at the ill-lit image of a paramedic helping a woman from the wreck. ‘Could that be his wife?’

Omar roared with laughter; his English hadn’t deserted him completely. The woman was flashily attired, with glittering pendant earrings and a tight-fitting evening gown. Tehran certainly had its Gucci set, and behind closed doors – or the tinted windows and dividing partition of a limousine – even the most respectable woman was no longer bound by the rules of hejab. But looking again at the still, he thought perhaps that was stretching the bounds of probability.

‘Okay, so it’s his mistress. Or a prostitute.’ Even so, Martin was a little surprised that Omar and his friends would treat such a revelation with anything more than cynicism. Dozens of young Iranians had told Martin that their rulers were two-faced hypocrites, moralising endlessly in public while they embezzled oil money and lived like kings. One student had shown him a famous cartoon: in the first panel, the despised former Shah cupped his hands beneath a torrent of gold falling from the sky, with just a few stray coins spilling out from between his fingers to reach his subjects below. In the second, a glowering, bearded mullah stood in the Shah’s place – and this time every last coin was caught, with nothing slipping through.

Omar wiped tears from his eyes. ‘Bebin!’

Martin looked at the picture again, wondering what he was missing. The woman was statuesque, with striking bone structure – was she a famous actress, or a singer? Perhaps it was just the poor quality of the image, but there was something theatrical, almost mask-like, in the excess of make-up she was wearing-

‘Mibinam,’ he said. ‘Mifahmam.’ He understood, now, why Omar had woken him.

Hassan Jabari, former government prosecutor and current member of the Guardian Council – the body that had declared more than two thousand aspiring candidates for last month’s election to be insufficiently loyal to the principles of Islam – had just been caught in his chauffeured Mercedes Benz in the middle of the night in the company of a glamorous, begowned transsexual.

‘Berim be-’ Martin struggled.

‘Hospital?’ Omar suggested.

‘Dorost,’ Martin agreed.

Behrouz, Martin’s translator, had taken a fortnight’s leave to visit his parents. With the non-event of the election over and half the country shut down for Noruz, the Persian New Year, Martin was officially on leave himself, but he’d decided to stay in Tehran and catch up on paperwork.

As they drove into the city, Martin contemplated the task ahead of him with unease. He recoiled from the prospect of treating anyone’s sex life as news – least of all when there was a potential death penalty hanging over the participants – but the email was already circulating, the revelation a fait accompli. The real story now was not Jabari’s behaviour, but the way the regime and the public would respond to the exposure of his hypocrisy.

‘We should call him “Hugh Grant” Jabari,’ Omar suggested – rather proudly, as if the time was long overdue for an Iranian celebrity to grab the attention of the international tabloid media.

‘I’m pretty sure Hugh Grant was caught with a woman,’ Martin said.

Omar racked his brain. “‘Forty-Eight Seconds” Jabari.’

‘Keep this up and you’ll be hosting the Oscars.’

Omar owned a shop that sold consumer electronics – and the odd bootleg DVD under the counter. His English had come back to him completely now, but Martin wished he wasn’t so reliant here on Omar’s help. Omar was a partisan player in all this, an unashamed pro-reformist; Martin was grateful for his tip-off, but it would be both naïve and unfair to expect him to act as an impartial colleague, like Behrouz.

They drove down Taleghani Avenue, past the ‘Den of Espionage’ formerly known as the US Embassy. The walls of the compound were emblazoned with bombastic slogans – helpfully translated into English for the edification of tourists – and a series of murals that included a skull-faced Statue of Liberty that would not have looked out of place on a Metallica album. Even at this hour Tehran’s traffic made Martin nervous, with the ubiquitous Samands and old fume-belching Paykans weaving between lanes without warning, and motorbikes zigzagging into every tiny space that opened up before them.

As he turned his company Peugeot Pars into the cramped hospital car park he hoped they hadn’t arrived too late. In a perfect Orwellian police state, Jabari’s companion – and every witness to the crash – would already have vanished without a trace, but Tehran was a very long way from Cold War East Berlin. He doubted that Jabari’s double life had been an open secret among the rigidly pious regime’s upper echelon, and while elements of VEVAK, the intelligence service, might have known about it – keeping it on file for a time when a political favour was needed – it would not surprise him in the least if they had not yet even heard about the accident; the email had been distributed in encrypted form to a relatively small number of people. In the first instance Jabari’s driver would be charged with keeping everything under wraps, but if he were out of action, who would call in the fixers?

Martin turned to Omar. ‘So what does a paramedic do when he comes across a man dressed as a woman?’ He was assuming Jabari’s companion was pre-operative, though that wasn’t necessarily the case; Ayatollah Khomeini, no less, had issued a startlingly enlightened fatwa in the eighties, declaring that gender reassignment surgery was a perfectly acceptable practice.

Omar said, ‘For a heroin addict lying in an alley, who knows? But for this, I think he acts like he doesn’t notice. Why make te-rouble?’

Martin pressed the heels of his palms against his eyes. A male paramedic had an excuse to play dumb, but what happened when a female doctor examined the patient more closely? Notwithstanding Khomeini’s ruling, there was no guarantee that a man who took oestrogen and put on an evening gown was going to sail through the segregated medical system without igniting some form of commotion.

‘Are you sure you want to do this?’ he asked Omar. ‘If I screw things up myself, the worst anyone’s going to do to me is deport me.’

Omar looked irritated. ‘I want you here as a witness, but no way you could do it alone. Berim.’

It was a busy night; Omar spent ten minutes in a queue at the reception desk before a polite but harried woman could speak with him. Martin stood at his shoulder and tried to follow the conversation without letting the effort show. Omar said his wife had been in an accident. What was her name? Khanom Jabari: Ms Jabari. Martin’s skin crawled at the audacity of it, but this scenario offered them their only chance. Iranian women kept their family names when they married; Hassan Jabari’s sister would remain Khanom Jabari. If Jabari’s companion was still passing as a woman, it would surely be too risky to register as his wife, so claiming to be his sister was the only respectable option left.

The receptionist typed something into her computer, then glanced up at Omar. ‘Shokouh Jabari?’ She gave a date of birth.

‘Dorost, dorost,’ Omar replied impatiently, as if these details were trivially familiar to him. Martin waited to see if the receptionist would ask Omar to confirm his own name against a recorded next of kin, but she had better things to do. ‘Bekhosh shishom,’ she said. Ward six? Omar was already walking.