Royal Ascot, which has a heritage stretching back nearly 250 years, is one of Britain’s must-attend events – not only for the quality of its racing, and the £4million in prize money on offer, but also for the fashion spectacle it provides.

The royal meeting demands getting dressed up in your best bib and tucker, and in the Queen’s Diamond Jubilee year, organisers of the famous summer race meeting have issued new guidelines as to what can and can’t be worn.

Charles Barnett, chief executive at Ascot, said: “We have worked extensively with experts in the world of fashion to define better what formal dress means, with the overarching intention of being as helpful as possible to our visitors and assisting everyone in understanding what is expected and, we believe, cherished about the dress code at Royal Ascot.

“It isn’t a question of elitism and not being modern in a world where there is less and less requirement to dress smartly – far from it. We want to see modern and stylish dress at Royal Ascot, just within the parameters of formal wear, and the feedback we have received from our customers overwhelmingly supports that.”

So make sure that you know the dress etiquette to a royal race day at Ascot before you set off for Berkshire in your cherished Manolos.

The Royal Enclosure Out are fascinators. Only hats are allowed – no ifs, no buts – and should be worn by women in the Royal Enclosure. However a headpiece which has a base of four inches (10cm) or more in diameter is acceptable as an alternative to a hat.

Dresses and skirts should be of modest length. Knees can be shown at a pinch, but you can’t go any higher than just above the knee. Miniskirts are a definite no, no.

You can show bare shoulders, but dresses and tops should have visible straps – and the straps should be 1in (2.5cm) wide or more. Strapless, off-the-shoulder, halter neck, spaghetti straps, sheer straps and dresses with a strap of less than 1in are not permitted.

Jackets and pashminas may be worn, but dresses and tops underneath should still comply with the Royal Enclosure dress code. Trouser suits are welcome if they are full length and of matching material and colour. And don’t show your midriff! (As if you would!).

For the gentlemen, black shoes are de rigueur, with your black or grey morning dress – no other colour will do. And your ensemble must include a waistcoat and tie. Those with a penchant for cravats can go hang.

And don’t forget the top hat! It’s part of the morning dress and must be included – and you don’t have to dither over colours either – you pays your money and you takes your choice – grey or black. But don’t worry, you won’t have to wear the towering structure on your head all day! According to the Royal Ascot 2012 dress code, “a gentleman may remove his top hat within a restaurant, a private box, a private club or that facility’s terrace, balcony or garden. Hats may also be removed within any enclosed external seating area within the Royal Enclosure Garden”.

But don’t get any funny ideas about personalising your topper with coloured ribbons, bands or any other item, thinking it’s a wizard wheeze. The customisation of top hats is no laughing matter.

The Grandstand Enclosure Headgear, whether it be a hat, headpiece or fascinator, must be worn by the women who will be cheering on their bets from the Grandstand.

And let’s have a touch of decorum pleeeze! A strapless or sheer strap dresses and tops won’t get you past the stewards. Jackets and pashminas may be worn, but the dresses and tops underneath should still comply with the Grandstand admission dress code.

If you’ve turned your wardrobe upside down and can’t find a suitable dress or skirt to wear and are considering sporting your smartest pair of trousers instead, bear in mind that they must be full length (no cropping permitted) and worn with a permissible top.

Midriffs must be covered – who wants to see your stomach anyway? And shorts are definitely not permitted.

The men’s dress code in the Grandstand also cranks up a notch this year. They will be required to smarten up and wear a suit and tie – not just a shirt and tie – that was so last year.