Deep in the recesses of Bradford's National Museum of Photography, Film & Television lies the most unlikely collection of photographs: a comprehensive record of the fashions which dominated Royal Ascot in the Thirties.

These pictures (which come from the archives of the old Daily Herald) are of as much value to fashion observers as they are to social historians. Here, ruddy-faced "commoners" peer over a fence at the fluidly draped dresses and elaborate headwear of the moneyed. There, an outfit so overburdened with flounces and frills that it seems positively Victorian walks alongside another that wouldn't look out of place in the Royal Enclosure, c1997. Look closely at these pictures and you realise how bias-cutting a la John Galliano, Missoni stripes and Pucci prints - all commonplaces of mid-Nineties dressing - have their roots entwined in Thirties style.

Then another realisation hits you: how little dressing for Royal Ascot has changed. Though smart trouser-suits were allowed into the Royal Enclosure in the Seventies (and although a couple of years ago one woman racegoer was let in in full male morning dress and black silk topper, with only a lacy cravat as a concession to her femininity) the real changes between now and then are really more a question of detail. You're less likely to see gloves today, or tights - even Diana, Princess of Wales, has been known to leave her sheers back at the palace. Otherwise at Ascot in 1997 women will wear neatly matching dresses, coats and hats - much as they did 60 years earlier.

Ask designer Tomasz Starzewski, who has made many an Ascot outfit for his clients. "In the Eighties there was an incredible use of skirt suits in heavy fabrics with big shoulders and big buttons." And now? "The look is softer with flowing fabrics, but still based around dresses and coats."

The reason for this sense of deja vu is largely due to the strict dress codes. Each year when a successful applicant for the Royal Enclosure receives their voucher from St James's Palace, they are issued with a set of guidelines on the do's and don'ts of dress for entry into the hallowed ground. Any transgressor is firmly turned away. The guards have no pity. No matter how much has been spent on that fab new dress (to attend Royal Ascot demands a tremendous outlay of money, as serious race-goers will wear a different outfit for each day and must have alternatives to hand if temperatures dip ), the custodians of the gate will not flinch. These are the fashion police made flesh: checking skirt lengths with their rulers (never shorter than just above the knee), banning entry to plunging necklines and bare shoulders alike.

Dress codes are also compulsory for men. Either wear service dress, or a black or grey morning suit with top hat; certainly do not attempt to carry an umbrella espousing the virtues of any club, drink or designer label. And whatever the heat, never, ever shed your jacket and hat.

Actually, in 1969 there was a slight relaxation of the regulations for men, briefly allowing the wear-ing of lounge suits in the Royal Enclosure, but it received the cold shoulder from racegoers and was dropped the following year. "I believe black or grey is the perfect backcloth for the girls," explains Manny Silverman, former managing director of Moss Bros. Although I am happy to see a coloured waistcoat; it doesn't distract, but enhances the overall look."

In the end, whether in the Thirties or the Nineties, Royal Ascot has always been about dressing up and showing off - the clothes-horses versus the four-legged variety. And after all, beautiful dresses and hats can come as a welcome distraction, says couturier Isabell Kristensen: "If I've lost a bet too many times, I can always go and look at the clothes instead."

! `Daily Herald' archive pictures appear courtesy of the Science & Society Picture Library at the Science Museum in London.