It is the 18th year of the Islamic revolution. And although as a traveller you are often told the revolution is crumbling from within, its outward symbols are as prominent as ever. Women must, without exception, hide their hair and every curve of their bodies in garments known as hejab, and many cover themselves completely in chador. The garments have to be black or a neutral colour, and a group of women walking down the street tends to look like a flock of weird crows.
Tehran is full of ardent murals 100ft high and more, extolling revolutionary virtues. High up on billboards, white-bearded mullahs gaze sternly but beneficently, like Father Christmas's serious older brothers. A handsome young soldier, mortally wounded in the war with Iraq, smells a rose 3ft wide, held by an angelic child. Behind them visions of the garden of paradise - an ecological impossibility given the city's air pollution - blossom across the wall of high-rises.
These uncompromising facades of revolutionary zeal hide a very different story. Like Tehran's underground railway, which is forever under construction and never seems to get any nearer completion, the revolution is a rickety compromise with an uncertain future. A visit to Ayatollah Khomeini's mausoleum is perhaps the most poignant place to see this. It is one of the biggest construction sites in the modern Middle East, and it looks like a combination of Disney's magic castle and Terminal Four at Heathrow. Open 24 hours a day, it is intended as a place of pilgrimage for people the world over, but especially for the mostazafan, Iran's oppressed masses who were his most ardent supporters, and who supplied a frenzied crowd of more than 2 million at his funeral.
One of the most potent myths of the revolution is splendid isolation and independence. Iranians have a well-developed sense of grievance about foreign interference, and with good reason: for the past 300 years Iran has been as a pawn in the games of other nations. But the revolution in 1978 and the terrible war with Saddam Hussein's Iraq from 1980 to 1988 marked a coming of age. It is thought that 1 million Iranians, many of them young volunteers, were killed in the conflict. But, despite some terrific blunders, the country held its ground without any foreign help. By contrast, Saddam, an enthusiastic gasser of women and children, enjoyed extensive support from the Soviet Union and all the major Western powers including the US, which provided him with crucial air surveillance technology. There's no doubting the magnitude of Iran's achievement in staving him off.
But that was then. Now, Iran is a young country. Half the population is under 20. They don't remember the supposedly evil times of the Shah, and even the war against Iraq seems like ancient history. An average salary is now less than pounds 100 a month, no more than a quarter of what a family needs in Tehran. The gap between the rich and the poor - one of the main causes of the revolution against the Shah - is painfully obvious, and shows every sign of growing. So it's hardly surprising that many young Iranians are turning their backs on ideology and are looking for a place to party. Sometimes it seems they've already found it, right under the nose of authority. Beside a high-rise block of flats displaying a giant portrait of Ayatollah Khomeini I came across a funfair in full swing. Young girls, dressed in full black garb, were whizzing around at high speed on a whirligig, whooping with delight. The big issue for young people everywhere - how boy meets girl - is made doubly difficult in Iran by rigorous separation of the sexes in public. Even tiny signals can be dangerous in the wrong circumstances, as I found myself when I casually removeda ja cket on entering a shopping mall, revealing bare arms. Within a few seconds two heavily bearded gentleman appeared from nowhere and told me in no uncertain terms to put my jacket on again. My friends said later that we were lucky not to have been hauled into the police station. If you're caught just holding hands with someone who is not a brother or sister you can end up spending a rough night in jail. Some young men in their last year of high school told me they would get hold of the rota of the local police station so they'd know when it was safe to meet girls in the parks. There are few places where young people can talk frankly in public. Among them are the city's handful of Armenian coffee houses. At one of these I joined some students - engineers, mathematicians, medics. Our table was attended by ancient waiters, dresse d in the elegant uniforms of a more liberal time, who served us excellent coffee - a rarity in Iran. Conversation sparked over famous poets of the past and musicians of today. But when I asked how they felt about the future, my friends smiled sadly,and talk trailed off into silence. Yet for all their uncertainty they remained open-minded and hospitable. And it was this warmth and welcome that made Tehran such a rewarding place to visit.
British Airways (0345 222111) and Iran Air (0171-409 0971) fly three times weekly between Heathrow and Tehran. The lowest official fare on BA is pounds 1,058.50. A discount ticket on Aeroflot via Moscow from IMS Travel (0171-224 4678) costs pounds 425.50.
Few tour operators specialise in Iran. Jasmin Tours (01628 531121) has a programme of group tours; the company can also make arrangements for individual travellers.
Contact the Visa Section of the Consular Department of the Embassy of the Islamic Republic of Iran, at 50 Kensington Court, London W8 5DD (0171- 795 4922, 2-4pm).
All parts of the body, except for the hands, feet and face, must be covered when in public, and outer clothing should be loose-fitting.
The Howeyzeh Hotel (see page 10) on the corner of Nejatollah and Taleghany Avenue (00 98 21 894 817) is one of the few remaining good-value hotels in Tehran.
The most recently published guidebook to cover Iran is Lonely Planet's Middle East (pounds 13.99).