And they're off!

It's a good start by The Bookmaker who's left Sad Punter for dead, trampled underfoot by Landed Gentry on this, the opening day of the Cheltenham Festival. And The Jockey is being pressed hard by The Trainer's Wife with The Trainer in hot pursuit. Trailing by a lolling head is a drunken Young Aristocrat who's being led a merry dance (non-runner) by Media Baron with Helicopter Boy bringing up the rear (and a liquid breakfast). We hand you over now to our social commentator, Stan Hey, who finds the most glorious event in the racing calendar running true to form...

It's a good start by The Bookmaker who's left Sad Punter for dead, trampled underfoot by Landed Gentry on this, the opening day of the Cheltenham Festival. And The Jockey is being pressed hard by The Trainer's Wife with The Trainer in hot pursuit. Trailing by a lolling head is a drunken Young Aristocrat who's being led a merry dance (non-runner) by Media Baron with Helicopter Boy bringing up the rear (and a liquid breakfast). We hand you over now to our social commentator, Stan Hey, who finds the most glorious event in the racing calendar running true to form...

The Trainer Cheltenham is just about to tell you that you're not as good as you think you are, but you can bluff this out as always.

The Trainer's Wife You've groomed the horse but now your husband wants to borrow a grand from your father's bequest for a bet - but on another horse in the same race.

The Sad Punter You have badges from every racecourse in Britain dangling from your binoculars but you still can't find a winner at the Festival.

The Landed Gentry The first chance to get stuck into the port since Christmas. A whisper tells you that your IQ has been deemed too low even for Jockey Club membership.

The Jockey The focus of attention, most frequently that of the Stewards for lashing your horses with the whip. Protest innocence. But you know a girl who'll demonstrate that it does hurt.

The Bookmaker Just back from Barbados, and God throws you thousands of punters who donate their money to you. Life is sweet.

The Helicopter Boy Brilliant arrival, and boozy day to follow. But on the flight back to London you forget that the helicopter has no toilet facilities.

The Media Baron

More likely to be "new" media than "old". You love the view from your hospitality box and are amazed that your mobile can still get a signal out here in the country.

The Owner Usually male and middle-aged, an early retiree or recipient of a PEP windfall. Buying the horse was a substitute for the mistress you can no longer attract or afford.

The Young Aristocrat Drawn, like lemmings, to Cheltenham by centuries of genetically-ingrained habit, even though you think racing is beastly.

No fewer than 150,000 people will be descending on Cheltenham's Prestbury Park racecourse from this morning for three days of serious gambling, hard-core drinking, sexual intrigue and generally excessive behaviour. They will also be watching 20 fiercely competitive races featuring the best horses in the National Hunt game. To the regulars it is known simply as the Festival, but what it means to each individual who attends can be as wildly different as smoked salmon and jellied eels (both dishes will be available). Underpinning everything will be a widespread social coding that defines many more types than Royal Ascot or Henley could. Quite simply, all sections of British and Irish life will be there, though not necessarily as you would know them.

For Cheltenham boasts infinite subtleties in its dress codes and offers race-goers many disguises that they can borrow for the three days, in much the same way that you can hire a car. With the right suit and badge, you can pass for a member of the landed gentry; or you can "go native" by wearing a shamrock in your lapel and borrowing an "Oirish" accent that you picked up by watching Father Ted. Indeed, renting a dog-collar from a costume-hire shop is an even better move, as everybody buys the priests a drink, and nobody stops you from going wherever you like. But you will have to know how to "cross" yourself properly before a race: otherwise you'll be quickly rumbled as an impostor.

A rough breakdown of the daily crowds at Cheltenham would probably reveal that 50 per cent of the people there either live in the countryside or pretend to themselves that they do. That means taking the four-wheel drive to the course and spraying it with mud and horse manure to make it look convincing. You will also need lots of stickers for display on your rear window - everything from "The Countryside Matters" to "Support Your Local Hunt". But beware the anti-bloodsports activists patrolling the car parks armed with sticky-backed letter Cs for satirical purposes.

Once in the car park, the tailgate must come down and the picnic be displayed for all the race-goers around you to see. Game pies, breasts of duck, pots of pickles and mustard give the right impression. Scotch eggs from Waitrose do not. Drink claret rather than champagne. It is also vital that you talk in an extremely loud voice. It not only suggests that you have authority but also that you have a house so large that personal communications can be conducted only by shouting. Don't forget also that being on display at Cheltenham is an affirmation of the power of your family. So get the boys out of Marlborough for the day and bring your sister, brother and wife, but never your mistress or gay lover. This "gathering of the clan" image is a powerful statement of dynasty, so flash the signet ring on the "pinkie" and drop names about who's coming to your house party.

Whether you're "real" country or fake, the dress code is the same. Tweed, and lots of it, preferably in green or brown. You can throw in a pair of red socks to make yourself look racy and modern, but joke ties with a hula dancer or horse's head are a no-no. Remember to lift your trilby when greeting female acquaintances, and it's just two kisses on the cheek, not the French-style three. You must always be cheerful and loudly upbeat, even if your Lloyd's syndicate has long-since gone belly-up, or if number-one son and heir is spending three grand a month on grade-A Charlie.

When watching the races, you must either have access to a box or pretend you have. That requires a bit of wandering off and blustering your way past stewards on stairways, but if you look pukka and smile at them, the "jobsworths" will quickly touch a forelock and wave you through. You must place your bets either with Tote Credit or with a respectable bookmaker on the "rails" between the Member's Enclosure and Tattersalls. Don't go into the betting-ring itself because real country folk don't have a sense of ironic detachment about low-life types. They just don't like them, full-stop.

Of course, in the modern age, Cheltenham has also become a Mecca for the corporate hospitality set, be they from traditional industry, the media, the City or even the spanking new dot.com companies who are desperate for any kind of material that they can input on their services. The City boys mostly arrive by helicopter, landing on the infield. As they walk to the stands they find that their thoroughly urban slip-on shoes are being tugged off their feet by the mud. From the moment of touchdown, the mobile phones must be turned off, and the headsets with built-in microphones folded away. This is an away-day from the office, so forget the Ftse and get into the Bolly. Enjoy the rare experience of being out of an air-conditioned environment. If you have brought female colleagues along, remember that all the latest sexual harassment cases in the City are going their way, so control your spring fever.

City boys must bet in the wilder reaches of the Tattersalls ring because it will remind them of their younger days on the floor of Liffe or the old Stock Exchange, when one flick of the nostril bought you "two mill of copper futures". If you want to be flash, bet with £50 notes, but be aware that the bookies are now tooled up with forged-note detector pens, laptop computers and constant ear-piece communications. They have been dragged into the 21st century, and you may be able to bond with them by giving helpful hints on touch-screen dealing. Finally, the City type can, with impunity, get completely off his face with drink, because that's exactly what the public expects of him.

For anyone in the new media - especially young women who work for independent film or television companies - Cheltenham at Festival time can seem a brash, male-dominated event. But remember that you are there to be iconoclastic, so don't be afraid to play up to the "new lass" image. The boys will love it, and even the Old Tweedy types may raise a smile at your bad-gal behaviour. So yatter on the mobile phone as much as you like. Get behind Channel 4's betting guru John McCririck and wave at the camera. Give him a big snog if you really want to make a stir. Or shout out: "Come on, John-boy, get your tips out for the girls!"

You must also drink lots and smoke a suggestively fat Cuban cigar. Don't be afraid to ask: "Which one's Lester Piggott?" when the jockeys come out of the weighing-room, because people will think you're being cute. If you find yourself being chatted up by a jockey - and they are called "jump" jockeys not just because of the fences they have to clear - tell him that you'll need two of them to make it worth your while. That will frighten him off.

Meanwhile, the new media barons will be taking the chance to network at Cheltenham, talking wireless application protocols and MP3. The fact that Cheltenham doesn't insist on men wearing ties is a boon because you never wear one anyway. Just stick with your favourite, tightly buttoned-up shirt in Iranian ayatollah-black. You must place your bets via an Internet link on your mobile phone to an offshore bookmaker in Gibraltar. You will carry a full set of business cards, complete with your e-mail address, so that contacts can be made and followed up.

As you will be drinking only a mineral water and ginseng tonic, you will be able to recall the days when you played Totopoly as a child. You will weep in remembrance of it, and then write a column about the experience for a magazine. You will also set about acquiring the all-media rights to the original game, announcing loudly to your staff: "Who needs to go to a course when you can play virtual horseracing on your PC?"

Even if you are going to Cheltenham to punt rather than pose, a certain amount of ritual and behavioural adjustment can be made. You can play the wild Irish rover, haircut like a burst mattress and jacket flecked with foam, but when you get your 30 grand in cash out of the RyanAir carrier-bag and lump it all on Istabraq, you can see the instant fear in the bookie's eyes. You can also be Mr Cool with the RayBans and the diamond ear-stud, watching the computerised boards until the last seconds before "the off". Then you steam in with your £5 each way on the odds-on favourite. The bookies will be terrified.

For a small section of people, the Cheltenham Festival is more about work than recreation. It is a terrible time for owners, who have spent the whole year dreaming of leading their own horse into the winner's enclosure and being handed a trophy by the Queen Mother. It is also a terrible time for the trainers, many of whom have been lying through their teeth to the owners about their horses' prospects. Now that it's "showtime", you will have to scroll through your index of excuses - "wrong tip" or "the ground was too firm", or the daring "they just went too quick for her".

The trainers' wives, charged with running the yard for the week, feeding the staff, keeping the owners sweet and bailing the stable-jockey out of Cheltenham police station after his drink-driving charge, will also have a fraught time. Cheltenham has nothing to offer you except the chance to run your eyes over the other trainers and see if any of them fancy an upgrade on wife number one.

For the jockeys, the men at the business end of Cheltenham, the Festival is a mixture of sheer terror and Hell-Fire Club antics. Most of your early-morning work riding is off for the week, so you can stay and paint the town red, showing the correct riding position to the lap-dancers at the Embassy Club, who will remember your antics from the previous Festival and present you with a paternity suit.

Finally, there are the many thousands of ordinary, well-dressed National Hunt enthusiasts who have been following the season as its foul-weather friends, who quietly resent the fact that 49,000 of the people at Cheltenham today weren't there when it was slashing with rain at the December meeting. For you, the silent majority, the racing itself is more than enough.