“Now that is just what not to wear,” the two ladies from the Royal Enclosure tutted from underneath the pastel brims of their expensive hats: “Just wrong. Just not Ascot.”

One had the word “baroness” on her name tag, and the other was dripping in pearls, so both felt themselves more than qualified to comment on the girl passing by in the Lycra micro-dress. “Last year, there were an awful lot of young drunken ladies lying on the lawn showing their bits to passing stretched limos. I do hope this year is better.”

So, too, do the organisers of Royal Ascot. The distinctly unregal attitude to formal daywear among last year’s racegoers prompted a clarification of the dress code for the most prestigious event in the country’s horseracing calendar. It came complete with a reminder that knickers should be worn but not seen, dress straps should be at least an inch wide, and streaky tan lines are definitely not de rigueur.

Ladies attending the Royal Enclosure on the first day of proceedings yesterday afternoon were under strict instructions that “only formal day dress with a hat or substantial fascinator will be acceptable”.

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For men, it was top hat and tails, waistcoasts obligatory. And the fashion police were out in their numbers to enforce it. Self-appointed arbiters of taste, such as the baroness and her friend, seemed content that due respect was being paid to the new style rules.

At the main entrance, it was up to the veteran steward Derek Shergold – or Shergar, as he is nicknamed – to maintain sartorial standards. “We’re here to meet and greet, and watch out for the right outfits. People pay an awful lot of money to come to this enclosure and it is part of Royal Ascot to maintain the dress code, which has already lapsed in other race-courses.” Culprits, he says, are politely referred to the dress code on display. “Even if a gentleman hasn’t got a waistcoat on, I have to say sorry,” explained Mr Shergold, himself immaculate in a grey top hat, with a white rose in his buttonhole.

Luckily, he added, there had been no repeat of the previous year – “one woman I know stooped to pick up a racing card she had dropped and both her boobs fell out”.

A daily fee of £82 and sponsorship from a member who has attended at least four times previously are required to enter the Royal Enclosure.

With the exception of the girl in the Lycra minidress, the stewards said that no underwear had been on show so far. Certainly, glancing across the lawn, the only St Tropez tans on display were those acquired from a yacht, rather than the bottle.

Some rogue outfits did slip through, however. “Now she should have been stopped,” Mr Shergold instructed his team, pointing to the woman with offending bare shoulders. But it was too late. She was through, mingling with the Henry Esquires and their well-heeled wives, the sight of her strapless dress already lost in a colourful riot of overpriced chiffon.

Neither was there a rule barring the man with neck tattoos between his top hat and tails. Mr Shergold decided to be equally generous to the woman with the boundary-pushing hemline. “It was nearly two inches above the knee, but she was well turned out, so we’ll let it go.” It turned out to be a wise decision, given that Princess Eugenie arrived in the Queen’s carriage with an even shorter hem.

On the other side of the barrier, no less pride and effort had been put into the outfits. Ellie Leech, 23, one of a group of graduate trainee managers from John Lewis, who was attending for the first time, said: “I think it’s great that the day has become more accessible for everyone. I was too busy to buy a hat but you can get some lovely occasionwear on the high street.”

This prompted admiring comparisons among the group of each others’ hats, and the realisation that one girl had left the plastic tag attached to her elaborate feather headpiece.

Nearby, Hayley, Bianca and Verity, sales assistants from Debenhams, defended their spaghetti-strapped dresses. “We’ve just seen a red denim dress – now that should be a definite nono,” said Hayley, over a can of Pimm’s. Then, behind a cupped hand, she whispered something seldom heard at the Royal Ascot of years gone by: “See that? That dress is from New Look.”

After a thorough assessment of inappropriate flip-flops and visible panty lines, they followed the crowds towards the course. Apparently, there was some racing going on.

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