On his way home from a recent Nato summit in Wales, Barack Obama made an unannounced stop at Stonehenge. The prehistoric monument closed early so that the president of the United States could soak up the atmosphere without being gawked at by day-trippers. He was given a personal tour by an English Heritage curator before continuing his helicopter journey to London. Describing the ancient stone circle as "cool", Obama told reporters that he had "knocked it off his bucket list". The president's sightseeing sortie might seem beyond the reach of ordinary mortals but his stopover was merely a high-profile example of a global tourist trend. A growing number of tour operators specialise in putting together one-of-a-kind adventures. Like buying a tailor-made suit, discerning clients - many of whom have been there, done that, and bought the vineyard - are willing to pay for a "made-to-measure" experience. Add a whiff of one-upmanship and it's easy to understand why this sector of the tourism industry is becoming increasingly popular. The high-end holiday market encompasses a pigeonhole-defying range of possibilities. A customised itinerary can mean gaining entry where doors are usually closed while neatly sidestepping the tourist herds. The best companies can fix up tee times on a Ryder Cup golf course or charter you a steam train in India. They'll arrange for a historian to accompany you around first world war battlefields or set up a meeting with the president of the Maldives to hear how climate change is affecting the low-lying archipelago. Firms that put together special-interest programmes usually give clients the opportunity to unpick and reassemble itineraries to suit individual tastes. Perhaps you're fed up with arriving at all the best sights at midday, leaving you with overexposed, washed-out photos. Someone a phone call away will be happy to tweak the tour so that you arrive in Vienna for sunrise and Budapest for sunset. The people responsible for creating these once-in-a-lifetime trips are known as travel designers. They're chosen for their area-specific expertise, passion for the outdoors and a flexible but diligent approach to holiday planning. And they're keen to bust a bespoke business myth or two. According to Kim Nixon, managing director of A2A Safaris, tailor-made tours aren't only for the super-rich. Nor do they have to be luxurious. "It's a misnomer to describe destination specialists as always more expensive," the South African says. "We can put together a top-quality seven-night African safari from Hong Kong for around HK$30,000." At the other end of the scale, however, Nixon says you wouldn't get much change from HK$120,000. This would include staying at the very best properties with all meals, drinks and internal (but not international) flights included. In these times of technology overload, booking even a simple holiday involves negotiating a bewildering array of information. Google "Buenos Aires hotel", for example, and you can expect to be overwhelmed. If only you could pick up the phone and chat to someone who knows the Argentine capital inside out. George Warren works as Latin America travel designer for Jacada Travel, which has a Hong Kong office. He has lived and worked in Buenos Aires and spent his free time hiking in Patagonia. This specialist knowledge, and the odd spot of hand-holding, is something Warren's clients are willing to pay handsomely for. As he puts it, "A Hong Kong travel agent may be cheaper but you're unlikely to find one knowledgeable enough to offer advice about climbing permits for the Andes or the best places to stop along the Inca Trail, in Peru." Evidence of Warren's willingness to go the extra mile came when he received a request for a combined birthday and wedding anniversary surprise. The trip, a romantic tour of Argentina, took nine months to plan. Secret email and bank accounts were set up and phone calls were kept to a minimum. The husband told his wife about the dream holiday on Valentine's Day, a few weeks before departure. For Adrian Bottomley, Hong Kong-based founder of specialist trekking firm Whistling Arrow, bespoke travel is about distinctive experiences rather than "dull as dishwater" luxury group trips that end up with a cocktail party on a beach. It doesn't get much more distinctive than his Rhododendron Explorer trek. "Earlier this year, I took a group of botanists into a remote region on the border between Yunnan province and Myanmar in search of rare plant varieties. We stumbled upon a valley of outstanding natural beauty swathed in rhododendrons, which was also home to over 300 plant species found nowhere else on Earth." His clients were delighted and their photos now appear on a number of rhododendron society websites. "The group plan to go again next year," Bottomley says. Whistling Arrow treks are not for the faint-hearted, however. The terrain in rural Yunnan is challenging. Routes often follow seldom-used and slippery hunting tracks and involve wading through small rivers. Bespoke travel is not always about being pampered. Regardless of how challenging the trip, people who book with luxury tour operators usually want the logistics and the legwork taken care of by professionals, leaving them free to enjoy the experience. Most crave an adventure but they want the safety net of knowing that someone has done the research in advance and is on hand (or a reassuring phone call away) if anything goes wrong. And it often does. From the commonplace - overbookings, transport delays and bad weather - to more serious hindrances, such as earthquakes and political upheavals, there are times when travel designers have to think outside the box. In 2010, Jacada Travel had a client booked from London to South America via Paris. The unfortunate passenger was unable to fly to the French capital as a result of the havoc caused by the Icelandic ash cloud, so the company paid for a London taxi to get their man to Paris in time for his onward flight. "If things didn't go wrong I wouldn't have a job," jokes Warren. "Not long ago, two pilots from the same South American airline got into a fist fight before take-off and the flight was cancelled. In this kind of situation we do our best to make our guests feel special. This means getting them on another flight as soon as possible, arranging an upgrade to an even more luxurious hotel - if there is one - and perhaps offering them a meal at a good restaurant." Sometimes requests can't be fulfilled at any price. Nixon, who has spent 21 years guiding in South Africa, Namibia and Botswana, was contacted by a family who wanted to explore the vast sand dunes of the Namib Desert, in central Namibia, and hoped to see cheetahs prowling past. They were disappointed to discover that the nearest big cats are in Etosha Game Park, hundreds of kilometres to the north. In recent weeks, a tenuous grasp of geography has led to clients cancelling African trips as a result of the Ebola outbreak. Nixon stresses that the safaris offered by A2A are mainly to Kenya and Tanzania - half a continent away from areas affected by the virus. Nothing fires up a designer more than the prospect of opening a map and discussing ideas and itineraries. So who are the ideal clients? Warren recalls a family of five who wanted to travel around South America for 10 weeks. The budget was considerable and he was given a blank canvas, which he filled with llama trekking in the Bolivian Andes, Christmas on Easter Island, a cruise through the Patagonian fjords and privately hosted lunches and tours with vineyards owners. The London-based travel guru has no problem booking clients on shorter tours although he tries to discourage a "one night here; one night there" schedule. "It's not long enough to get under the skin of a place," he says. For Nixon, being close to nature and engaging all five senses is an important aspect of any trip to Africa. "Getting away from game lodges opens up a world of possibilities," he says. "I could arrange for you to go canoeing down the Zambezi River for three nights, camping on the riverbank in pre-erected tents." He also has some advice for safari-goers wanting to avoid the long lines of tourist-filled jeeps that stalk, surround and intimidate the animals. "Crowds are at their thickest in the Mara River area of Kenya during the wildebeest migration in July but many people don't realise that the migration lasts much longer than a few days. One October I was at a camp in Tanzania with just three guests. We drove over a hill and were confronted with herds of wildebeest stretching into the distance. There was no one else there to witness what was an unforgettable scene." For clients wanting a more unusual African encounter, the Capetonian recommends Zimbabwe. "It's a sleeping giant in safari terms. If you visit Mana Pools before the rains, you'll see hundreds of elephants and predators. At present, safaris in the country are 30 to 40 per cent more affordable than in more established ecotourism destinations like Botswana," says Nixon, who explains that Zimbabwe is recovering from years of political instability. Bottomley feels an adventure trekking specialist has to be imaginative and willing to try new experiences, although he acknowledges it's becoming more difficult to find places that are really off the beaten track. "Twenty years ago it was easy to find undiscovered areas of Yunnan. Even Tiger Leaping Gorge wasn't very touristy back then," he says. He has a few exotic destinations up his sleeve, though, such as the Wakhan Corridor, a high mountain valley between Afghanistan and Tajikistan. He is also looking at the possibility of a winter crossing of Lake Baikal, in Siberia. "It takes about 45 days to trek across, camping on the ice and riding on dog sleds. From what I've read, it's about the closest you can get to a polar expedition." For Bottomley, extensive knowledge of the areas he visits is crucial. Contingency plans are drawn up that cover everything from alternative routes to assessing whether a rescue helicopter can be brought in should there be a medical emergency. "A lot of what we do tends to be quite expeditionary and it would be very unprofessional to go unprepared. If you're taking a group somewhere isolated then, obviously, the risks if something goes wrong are that much higher. At the same time, adventure travellers understand that when you go into remote regions, things don't always run smoothly. It's how you deal with the situation that is important. "I keep a smile on my face and look like I know what I'm doing." In an industry where the sky is the limit (literally, in the case of space tourism), turning dreams into reality can come at an environmental cost. Responsible, sustainable tourism is a stated goal for many of today's new breed of bespoke travel companies and designers are keen to highlight this aspect of their business. A2A Safaris like to work with companies or family-owned businesses that aim to minimise their carbon footprint, says Nixon, whose personal favourite is Ocean House, on the De Hoop Nature Reserve, in South Africa. The stylish property accommodates one group at a time. Conventional electricity use is limited; there are solar panels, water and waste recycling treatment plants and heat from cooking is converted and reused to provide underfloor heating. Best of all, though, the house overlooks the Indian Ocean and offers a grandstand view of the continent's greatest whale nursery. Hundreds of southern right whales migrate to the shallow coastal basins for the calving and nursing season. Bottomley stresses that Whistling Arrow treks engage and benefit the communities his groups pass through. "The money we spend goes into local pockets. We buy food in towns and villages before setting off. All our muleteers are Tibetan; we stay in locally owned hotels and hire fixers and assistants who, in turn, spend that money in the same markets and stores that we do." Warren recommends a carbon-friendly hike along the Inca Trail, 30,000km of misty mountains and valleys, up to Machu Picchu. Jacada Travel also offers a Tech Detox itinerary to Costa Rica, which features rainforest walks and yoga classes at a private reserve in the cloud forest. The trip is ideal for frazzled folk looking for some quiet time away from emails, texts and phone calls. Who knows, you might even bump into Obama.