It is a single strip of roadway dog-legged across north London with a remarkable roll call of billionaire residents in double digits and scores of multi-millionaires. There are a select few of what are called trophy roads in London, where properties change hands for many tens of millions of pounds. The street currently claiming the crown as <a href="https://www.thenationalnews.com/world/uk-news/2023/02/13/london-luxury-property-a-75m-mews-house-in-one-of-the-citys-most-exclusive-areas/" target="_blank">London's most expensive</a> is Avenue Road, a kilometre-long thoroughfare that stretches from the north end of Regent's Park up to Swiss Cottage underground station. According to a survey by the high-end estate agents Beauchamp Estates, there are 10 billionaires and 44 multi-millionaires who own <a href="https://www.thenationalnews.com/world/uk-news/2023/01/25/london-luxury-property-eaton-mews-south-in-pictures/" target="_blank">houses</a> or mansions on Avenue Road. The nationality of the owners is truly international, with <a href="https://www.thenationalnews.com/opinion/uk/2023/02/02/rate-rises-and-bigger-bills-the-gloss-has-come-off-my-london-property-purchase/" target="_blank">homeowners</a> from the UK, Egypt, Saudi Arabia, Nigeria, the UAE, India, Malaysia and China. Exclusive access to one of the properties, granted to <i>The National,</i> made it pretty obvious why this mansion was special, even on a road where every house is a dream. From the pavement outside, the mega-mansion that's listed at £110 million ($135.4 million) looks little different from the others that line this unique trophy road of billionaire's addresses. It has a very smart Georgian-style exterior, but nothing ostentatious. From the road it looks like a large, smart, brick-built house. It's only once past the front door that one can really appreciate the scale of the property and marvel at how so much has been cleverly designed into the space. The Beauchamp survey revealed that over the past three years, six new mansions have been built on Avenue Road with a combined value of £370 million, with the largest of these being a mega-mansion currently listed for sale for £110 million. In addition, over the next three years there are seven new residential development projects planned for Avenue Road, which have a combined value of £560 million plus. The current owner of the mega-mansion, a Saudi billionaire, bought the original house six years ago, and then bought the house behind it. The restructuring and reimagining of both houses now means that on this acre-sized plot on Avenue Road, there is a nine-bedroom main house and a connected three-bedroom mews house, together covering 30,000 square feet. Yet the property has never been lived in. “Our clients developed this house for their own use, but it took quite a long time and their situation changed and they decided that they weren’t going to need such a large house,” Rosy Khalastchy of Beauchamp Estates, the sole agents for the mansion's sale, told <i>The National</i>. There are, of course, elegant reception rooms, a study, a formal dining room and a music room. But as with many treasures, the wow factor in this particular house is underground. The subterranean spa has one of the largest private indoor swimming pools in London, with a ceiling 30ft high, complete with a chandelier that can be raised or lowered to suit the mood. But this is a spa and relaxation area that would not be out of place in one of the world's finest hotels, with a hammam, a sauna, a treatment room, hair salon and, naturally, a state-of-the-art gymnasium. The mansion also houses London's largest underground private art gallery; a spectacular 35ft-long space with specialist lighting, reinforced bomb-proof walls and bullet-proof skylights with automatic blackout steel security shutters. But all the way through the mansion, the most striking constant is the attention to detail and perfection. The marble in the two (yes, two) en suite bathrooms attached to the main bedroom is book-matched. That means it's been carved from a single piece of quarried marble, clearly visible by following the veins up the walls and down across the floor. The temperature control and air circulation systems in the games room, with its copper-rimmed snooker table, is perfect should the odd cigar be fired up. The acoustics in the luxury reclining seat cinema are of recording studio quality and while there is a cosy kitchen for the family to make a cup of tea on the ground floor, there's a huge professional kitchen on the floor below it, which would be the envy of many a Michelin-starred chef. Getting between the mansion's five floors (three above ground, two below) is made easier by the two lifts, one for the owners and guests, one for the staff. “The house is being discreetly offered to specific people," Ms Khalastchy told<i> The National</i>. "It's a question of finding the right person. Once you find the right person, I think they will love it and understand why it is the price it is.” Being situated on Avenue Road means that the mansion is just a three-minute walk from the 166 hectares of the Royal Regent’s Park and 25 hectares of Primrose Hill Park. Close by is St John’s Wood Village High Street, with its collection of trendy shops and restaurants. And it's just a short ride to London's celebrated West End shopping district. “The current mansions boom along Avenue Road is creating almost £1 billion worth of new luxury houses and mansions, a transformation which has elevated the profile of the address into arguably one of London’s most desirable destinations," said Gary Hersham, founding director of Beauchamp Estates. "Avenue Road is one of London’s finest addresses appealing to the same calibre of buyers as the likes of Kensington Palace Gardens, The Boltons, Cornwall Terrace and Holland Park." Development of Avenue Road itself really started in the 1820s and the original Victorian houses were owned the local gentry, merchants and successful self-made people including writer James Bickingham, the landscape painter William Collins and Herbert Spencer, the philosopher. Over the decades, people who have lived on Avenue Road include the film producer Sir Alexander Korda, the British billionaire Sir Philip Green, as well as members of the Saudi and Qatari royal families. More recently, a register of Avenue Road residents read more like a Forbes Rich List, as pop stars such as Rihanna and Robbie Williams, the boxer Anthony Joshua and various Silicon Valley billionaires have all called the street home at one time or another. But what has taken off in recent years is the trend to refurbish. Often the neo-Georgian facades cannot be changed, because the houses are in a conservation area, so the real transformations are not visible from the street. On Avenue Road, there is far more scope to create desired living space than there is in some of London's other prestigious areas, such as Mayfair and Belgravia, not least because most of the properties on Avenue Road are freehold, unlike Belgravia where many are leasehold. “In town, most of the houses are listed," Ms Khalastchy told<i> The National</i>. "You wouldn’t be able to create what you’re able to create with the Avenue Road houses. "You have the option to buy a larger, more opulent space that you create to your own taste. "This you would not find in Mayfair or Belgravia that easily. And, in Belgravia they might not give you the permission to do this kind of development, whereas up here [in St John’s Wood] you’re able to get it. Although a lengthy process, it’s doable. "A lot of people have slowly come further out and you’re still only 10 minutes from central London. Avenue Road offers you a lot more for what you can do with your money. “Avenue Road is special because you have the ability to have a wide house that is low build.” Nonetheless, the astute billionaire mansion-hunter normally needs patience when bagging a property on Avenue Road. It can take several years to get from purchasing through designing and redeveloping to personal specifications to actually moving in, even if money is no object. But Jon O'Brien, the founder and chief executive of the high-end property developers, Domvs London, aims to save billionaires time. “The most precious commodity that we’re saving all of these potential buyers is time," he told <i>The National</i>. "They’ve all got money, but we can offer them time, because they don’t have to buy a mansion, go through the planning process and then build it – they can just walk into it.” He's doing this by offering something unique on Avenue Road – a luxury development of 12 "mini-mansions" in three terraces on a plot of about half an hectare. It's a plot that UAE-based Select Group bought in 2020, with Domvs London as the site's joint developer. In the three years since acquisition, planning permissions have been acquired and detailed architectural designs made. The two derelict villas currently on the site need to be demolished and then construction can begin. Situated at 52 Avenue Road and designed by Domvs London's head architect, Shaun Knight, the development’s quintessentially British, white-stucco facades will replicate the grand Regency mansions of Regent’s Park and the work of celebrated royal architects John Nash and Decimus Burton. The 78,000-square-foot site is smaller than the usual Select Group project. The company currently has a £4.5 billion portfolio of developments and interests in the UAE, UK and Central Europe, including partnerships with leading hospitality brands like Six Senses Hotels, Resorts and Spas, InterContinental Hotels and Resorts and the Jumeirah Group. But Select's chief executive, Rahail Aslam, was very keen on 52 Avenue Road from the start. "This is a once-in-a-lifetime development opportunity," he told <i>The National</i>. "We're very firm about developing in ultra-prime locations and this hits our investment criteria. In terms of square footage, yes, it's relatively small for the group, but in terms of gross development value it's significant." As with everything on Avenue Road, attention to detail will be critical. Each of the 12 residences will have grand, volumetric proportions, with ceilings up to 3.65 metres high and floor-to-ceiling windows allowing an abundance of natural light. While giving the appearance of authentic Georgian style, the units will have various smart home automation capabilities and eco-friendly technologies and designs. For example, the development will make extensive use of geothermal boreholes, which go down between 120 and 200 metres into the ground, and for every unit of energy that goes into the system, three and a half to four units come out. “You won’t see the boreholes," Mr O'Brien told <i>The National</i>. "The costs of running this are significantly less than, for example, gas and it’s much more eco-friendly, because you do not put carbon into the air.” Other details include using a lime render on the walls, which aids in cooling, and specially designed stairwells within the units that funnel excess heat out. In addition to each residence having a private garden and a rooftop terrace, the development at 52 Avenue Road will also have a health and wellness spa, and five-star concierge service. The average residence at 52 Avenue Road will cover 5,750 square feet. It's predicted that the development will sell for £3,500 per square foot. That means an average price of at least £20 million for each of the 12 residences, which will vary in size and location on the plot. For Mr O'Brien, aside from the time-saving element, the individual gardens and roof terraces of each residence provide a unique selling point, for one specific reason: Covid. “Covid taught us one thing," he told <i>The National</i>, "people want their own private outdoor space. "Apartment living doesn’t generally give you that, unless you’re up on the penthouse level. And what we’re offering in this trophy road is something unique. “We’ve got significant interest already, because it’s such a unique offer.” The development will take another two and half years to complete. Ironically, the time it has taken to get all the planning permissions will be longer than the time required to construct the 12 mini-mansions at 52 Avenue Road. But at the high-end of the ultra-prime London property market, things are moving fast. “The high end of the market is flying," Mr O'Brien said. "People can have three, four or five homes in various different places, but London will be one of those places. It’s not mortgage driven – at the high end of the market, houses are simply commodities. "A commodity that they can also use and enjoy. Not dissimilar to a boat or an aeroplane, but better, because the house will appreciate in price.”