It's early on Thursday morning and a horse is making his way up the A9.

He gazes nonchalantly from the window of his horse box as Perthshire whizzes past. He is one of hundreds of horses, and riders, winding their way across the land to take part in the Blair Castle Horse Trials.

A few miles from the main road, at the end of a twisting singletrack, is the final destination. Blair Castle estate is surrounded on two sides by soaring hills and encircled by woodland with a white fairytale castle poking above the tree line, adding the finishing touch to a scene so perfect that even a film set designer wouldn't dare tweak it. It is the venue for what started as just another local horse event, but the four-day competition is now the highlight of the eventing calendar in Scotland.

Already there is a gentle buzz as tweed-clad visitors, most accompanied by at least one canine companion, peruse the trade stands. Most of the stallholders arrived here yesterday and Louise Smith-Kabaris of Stirlingshire Saddle Fitters has been trading since 8am. "We've already had a few riders running in before their event after straps or reins have snapped," she says.

While their saddlery business attracts riders throughout the year, at the horse shows much of the business is from the general public. In fact, a quick glance around the temporary canvas streets fanning out from the main arena reveals shops that extend beyond simply equine supplies; there is furniture and interiors, jewellery, clothing and art and even a stall peddling gold-flecked champagne.

"It used to be the Highland Show that everyone saved their money for and now it's Blair," says Louise, 46, who runs the business with Alene Telfer, 47, and has been coming here for 14 years. "They expect more than 40,000 visitors over this weekend. It just gets bigger every year. When Alene first came, a few years before me, it was just a few trade stands."

Part of the appeal, she believes, is the fact that there are competitions at different levels, from one star for the least experienced horses to three star.

Hosting events such as the Young European Championships in 2011 and securing the 2015 European Championships also raises the profile. Certainly, early gate numbers for the weekend are up slightly up on last year.

"The European Championships means all the teams from abroad will come, so you will get all the big-name riders, and people don't often get a chance to see that in Scotland."

However, this year horse trials in general have been affected by the summer's atrocious weather, which saw many events cancelled.

Louise adds: "There's not so many riders this year at Blair because they haven't had the runs. Their horses need to have a certain amount of clear rounds to qualify and because everything has been cancelled the entries have been low. It has been a dreadful year generally, although Scotland has done a little better than the south. We usually do 17 to 19 shows a year and we've probably lost five."

She estimates that horse shows bring in about one-fifth of the annual income of the saddlery business. "Because our year-round saddle fitting is very good for us, we've been quite lucky, but we'll probably notice a slight downturn in the takings from the shows. Everything is suffering."

One spectator who has missed out because of cancelled events is Anne Paxton, from Edinburgh, who is watching the novice ridden hunter class with her dog Tia. Anne has been riding since she was a child but is spectating instead of taking part as she's not been able to build up enough points because of cancelled competitions. "I'd rather be up there doing it, but never mind. I've come for the four days anyway to watch friends."

Horse trials or eventing competitions such as Blair have three elements – dressage, show-jumping and cross-country – and can take place over one, two or three days, with the champion being the rider who has the best overall score.

In addition to the main competition, today's timetable includes hunter classes, where traits and skills seen when out on a hunt are judged.

Over in another arena, the lightweight ridden hunter class is coming to an end. Gilly McCowan, riding Fusilier, which she owns with husband Andrew, is awarded first place. It's not even lunchtime but the day has already been a long one for the couple.

"We are based in Berwick-upon-Tweed so we were up at 2.30am," says Gilly, back at her lorry. The couple spend a large part of the year travelling from one show to the next.

"We enjoy coming to Blair because there is a good quality of horse," says Andrew.

In a neighbouring horse box is Diane Brash, from Linlithgow, who returns from the same class having been awarded second place on Rehy Striker. She is greeted by her father Tommy, who owns the horse, and her two-year-old niece Lexie.

A one-time show-jumper, Tommy, 64, latterly competed in working hunter classes. A well-known veteran of such events, he is also a judge. "Blair is great. We've been coming here for a number of years. Where do you get up in the morning and you've got hills on both sides and can watch the mist rising like this? And to wake up in the morning with a dram in your hand -" He tails off into a hearty laugh.

Daughter Diane, 39, has been involved with horses since she was two years old; the same age as Lexie.

By the end of the day, Gilly has won the ridden hunter championship, with Diane placed second.

Dressage takes place in the main arena and judges are positioned at four corners, sitting dry and cosy inside their vehicles. The stand is full and spectators have pulled their zips up against the hazy rain. It's just after lunchtime and the irresistible smell of fish and chips wafts over the spectators.

Next up is Wills Oakden, 22 – a portrait of straight-backed discipline he strides into the arena on Prime Time II, owned by Antonia Finch.

In 2010, he was the highest-placed Scottish rider in the FEI World Rankings, and at the Young European Championships here last year he won gold in the team event.

His team today includes his girlfriend Laura, aunt Frances Hay-Smith and his mother and stepfather, Liz and Mike, who come up to every event and groom for him. "It's good to have my family around me but I've got to pull my own weight, I'm not allowed to slack," he says.

This year he has an exhaustive schedule; riding on four different horses for four different owners. Competing at Blair has been a long-held dream. "It has an atmosphere like no other event in Scotland. When we were young, my auntie Frances and my father James used to compete here and we used to come up as kids and buzz around on our bikes and put on my dad's top hat and pretend we were doing dressage. We used to bring our ponies up and play around and it was what we aspired to do. It's what we build up to throughout the year."

Wills, 22, is based on the family farm, Dunbog, near Newburgh in Fife, with his father and aunt. "This is the biggest event in Scotland and it's where we want to go to showcase ourselves, in front of a home crowd, and they are amazing."

The recent success of the British dressage riders at the Olympics – winning three medals including two gold – has done much for equestrian events, he believes.

"It galvanises everybody. Not only the seniors that are here doing that, but right through to the grassroots. It's such an advert for us, particularly given how well the team has done. It has raised the profile of dressage."

While many of the riders here today will look after their own horses, some of the more senior – or wealthy – competitors employ grooms.

Robert South, 18, from Oxford, is a freelance groom accompanying rider Matthew Heath. It's his first time at Blair and he is looking after three horses. "I volunteer at Blenheim Horse Trials. It's nice there but I must say I like it here more. It's the views."

For Robert, the day starts at 6.30am. "My first job is to feed the horses and once they are fed I muck them out and then take them all for a 20-minute walk to exercise their legs, then give them some grass." Over the course of the day, he will take the horses out four or five times to get them exercised and eating grass.

"My job goes from mucking out to walking. If Matt wants to ride early I get the horse tacked up, and if he doesn't I get to do whatever I need to do; clean tack or get his gear ready. I'm always busy."

A keen rider, he hopes to one day have people grooming for him. "I love riding. I don't compete at the moment because I don't have a horse but I'd like to," he says.

At the moment he rides horses belonging to various people, many of whom he grooms for. "You don't need to be rich to do it," he argues. "There is another path. Not every rider has got money. If you are good enough, you work towards getting sponsors and the sponsors help pay towards the horse. They can either sponsor you as a rider, which covers all the horses you ride, or sponsor just one horse or sponsor a lorry.

"If you want to do it, you can do it whether you've got no money or money. Just keep trying. If you buy a nice young horse and you bring it on, that could have cost you £1000 and then three years down the line it could be worth £13,000. Then you buy a nicer horse and keeping building up."

With the scheduled events over by 5.30pm, the majority of visitors have left for the day. All that remains is the ceilidh in the main marquee to round off the first day.

"We don't crack the wine open until 5.30pm," says Louise Smith-Kabaris, with a broad smile. "If anybody is walking past and we know them, we'll give them a wee glass too. That alone, just sitting out the front in the sun, brings customers, so we can be open until 8pm."

With many teams and traders attending every year, there is a feeling of camaraderie. "A lot of people make it their holidays. They'll book a campsite or caravans or stay in their horse boxes. It's just a bit of a party time. You don't have to drive anywhere so you can have a wee drink. It's very sociable.

"All the traders are here overnight as well, and it's a lovely atmosphere. You're enclosed in your own wee world; you don't know what is happening in the real world; you go home after six days and wonder what is going on in the world." n