Of course it's fine to be ugly, as long as you don't expect to be loved

In the world of media modishness, it is fine to be post-something. Britain is post-Thatcher and post-imperial, the new celibacy is post-sexual or post-penetrative, the Polish government is post-Communist; culture has rolled down the aesthetic steps from post-structural to post-modern. But there's one marker which remains unpassed. Nobody is brave enough to be post-beautiful.

Scan a current icon, and you will see what I mean. There is Posh Spice, Sporty Spice, Scary Spice and so on. But where is Ugly Spice? There is a missed opportunity here, a chance to rubbish the last great orthodoxy of universal prettiness. Thinking over recent writing, I can recall only one novel, Fay Weldon's The Life and Loves of a She-Devil, which celebrates a woman with an ugly face. And even the She-Devil has to make herself beautiful in order to wreak revenge on the world which sneered at her.

A slice of history reminded me of this great injustice. The other day I met a Polish scholar, Dr Malgorzata Dabrowska of the University of Lodz, who handed me a paper she had written entitled "Sophia of Montferrat, or The History of One Face". People talk easily about Cleopatra's nose, and how history would have been different if it had been a few centimetres longer. Just possibly, an empire might not have fallen if Sophia of Montferrat had been granted another set of features.

By 1421, the Byzantine Empire was decrepit. Its final fall, the storming of Constantinople by the Turks under Sultan Mehmed II, was still some 30 years off. But there were feverish plans to reconstruct the Empire's diplomatic defences and in particular to overcome the schism between the Western (Catholic) and Eastern (Orthodox) churches. The Pope was persuaded by the Emperor Manuel II Palaeologos to allow the marriage of an Italian Catholic lady to his son and co-Emperor, John VIII.

The Pope's choice fell on Sophia of Montferrat. Her family, with its domains in the foothills of the Alps, had a background of close connections with past Byzantine rulers. She was 26 years old, slightly older than John, rich and probably rather well-educated - she may already have understood Greek. Off she went on a Venetian ship to Constantinople, and the mighty ceremony of marriage and coronation took place in the cathedral of St Sophia. John personally set the crown on the head of his new Empress, as she sat surrounded by eunuchs and wearing the imperial purple shoes. Days of public feasting followed. But, indoors, it was all going wrong already.

The trouble was her face. Chroniclers say that Sophia had a perfect figure, curly gold hair which went down to her ankles, fingers compared to crystal. But her face spoiled everything. For the Byzantines, her eyes, eyebrows, nose and lips were dreadful and disgusting. The historian Dukas reported that "from the back she looked like Easter; from the front like Lent".

There is no way to know what the problem was. Perhaps she had suffered from smallpox when younger. Or maybe the Byzantine court had its own eccentric criteria for beauty, and we - if we could see Sophia - would find her attractive in some un-classical way. At all events, the Emperor could not bear her appearance. The marriage was never consummated. Dukas adds that the Emperor did not love her, and others say that relations between them were bitter. But she remained in Constantinople for another five years, isolated with her ladies-in-waiting in some corner of the half- ruined Imperial Palace, until John declared the marriage over and sent her back to Italy in 1426. She spent the rest of her life in a nunnery, probably a worldly and comfortable one, near Alessandria. As for John, he at once married a brilliantly pretty princess from Trebizond, an Orthodox Christian like himself, and was reputed happy.

Dr Dabrowska quotes a Byzantine intellectual, Nicolas Kabasilas, who said that the appreciation of beauty leads to love, but that it was difficult to love the good if it did not have a beautiful appearance. She comments sadly that "John VIII was the follower of this view, for he never tried to seek good behind the ugly facade of his wife". And she ends with famous lines by W B Yeats: "...only God, my dear, / Could love you for yourself alone / And not your yellow hair."

Was Sophia a warm and wonderful person, who only suffered from "physiognomic challenge"? Nobody knows, but it would be horribly condescending to assume that she was a sweet creature "in spite of her looks". Perhaps, in the Weldon manner, her looks and their social consequences made a she-devil of Sophia of Montferrat. Or perhaps she was always an unpleasant character from her childhood, regardless of her face, as anyone has a right to be. The point is this: why do we persist in attributing interest and virtue to men and women who attract us?

I often pass through an Essex village called Ugley. Local folklore says that some years ago the Ugley Women's Institute rebelled and suggested that their village should be renamed. The lady of the manor is supposed to have retorted with a tremendous wigging, telling them that they should be proud to live in a place named after some forgotten Saxon settler called Ugga. My sympathy is with the Women's Institute. But what we really need is a cultural revolution to overthrow the moral values we attach to physical beauty or ugliness.

Montaigne, no romantic himself, was intrigued by the association of beauty with virtue. "In Greek, the same word embraces the beautiful and the good ... Aristotle assigned to the handsome the right to command, and held that those whose beauty approached that of the Gods were entitled to the same reverence. To those who asked why beautiful people should be sought out more often and more persistently, he replied: 'Only a blind person could put a question like that!' Most of the greatest philosophers paid for their schooling and acquired wisdom by exploiting their own beauty."

Small children have the opposite approach. A face that smiles convincingly at them is beautiful. But a woman with a hard expression, however stunning she is found by her peers, is an "ugly lady". Their impression of character determines their impression of beauty. To quote Montaigne again: "A face which is none too well put together can house a certain air of honesty and trustworthiness, while on the other hand I have sometimes read between two fine eyes the menace of a malign and dangerous nature."

Last week a woman was thrown out of Harrods on the grounds that she was wearing leggings. London journalists who rushed to the scene at once concluded that nobody would have applied the store's peculiar dress code if she had been slim and pretty. I expect they were right. But it is not enough just to rave against gnat-brained celebs who are worshipped because they have great bodies. And not much is gained by repeating priggishly that looks aren't everything. The point is to assert that human ugliness is not a nothing - the absence of beauty - but a very positive something.

Remember how George Orwell was struck by his own countrymen when he came back from Spain: "... the crowds in the big towns, with their mild knobby faces, their bad teeth and gentle manners..." This was a declaration of love. I remember the climax of a Polish pilgrimage which assembled half a million human beings to wait for the Pope. Beside me on the battlements stood a Polish lady. "My God," she said eventually, "what an unlovely people we are!" I will never forget the pride in her voice.