IT’S a place very few people know about, only accessed by a discreet, unmarked driveway at the corner of Heathrow Airport.

In fact, you will only ever get visit here if you are: a) very rich, b) royal or c) both. Or a journalist, like this one, who was granted special access.

Welcome to the Windsor Suites, the most secretive and expensive airport lounge in the world. It’s reserved for the wealthiest, most famous and most VVVVIP people on the planet with presidents, princesses and the Pope having passed through its doors, not to mention the Dalai Lama, Hollywood A-listers, plus the odd Silicon Valley tech titan here and there.

“Members from every royal family in the world have walked through our doors,” head of Heathrow VIP Priya Malhotra says.

“You are dealing with the world’s elite. If you open Time or Forbes, they are the people using the service.”

While most lounges offer limp sandwiches and warm glasses of sparkling, here you get bombproof glass, Andy Warhol paintings, French champagne and a private butler. And that’s just the start.

For years, this hideaway was invitation-only, reserved for visiting heads of states. Where else do you stash Vladimir Putin when he’s waiting for his flight? However since 2012, it has also allowed the seriously cashed-up, paying public.

Access to the lounge starts at $5055 for three guests for three hours — and that is only one way.

Similarly, stay longer than your allotted time and your bill automatically doubles. Most clients stay for only slightly over an hour, according to Ms Malhotra.

However, the guests it attracts aren’t exactly worried about the price. Some have been known to bring 100 people with them, booking out the entire facility before a flight, costing about $166,000 and counting.

And that’s only if you can get in. Demand for the lounge far outstrips availability.

The service starts when guests are picked up from home in a BMW 7 Series and delivered to the unassuming building on the edge of Heathrow Airport.

Inside, after being greeted by a bowler-hatted doorman (how much more British can you get?), VIPs are escorted to their own private suite where a dedicated butler is on hand to attend to their every whim, summoned by pressing a magical button. There’s a separate orchid-strewn lounge for bodyguards, nannies, assistants and various hangers-on. After all, who wants to mingle with the help?

Guests are also assigned a liaison officer who will handle all that pesky business of pre-flight paperwork and checking in.

The 14 suites vary in size but all are decked out with cashmere cushions, Italian leather lounges, designer coffee tables and impressive floral arrangements. On the walls are millions of dollars of hand-picked artworks that are rotated regularly, including pieces by Andy Warhol, Francis Bacon and Lucian Freud.

Special touches include bombproof glass and black netting placed strategically outside the building to shield guests from the unsightly airport — and any lurking paparazzi.

Bit of a dry throat? On offer is unlimited Dom Perignon champagne (a drop that starts at $220 a bottle) along with an extensive wine list.

Hungry? Dine on a three-course menu from Michelin-starred London chef Jason Atherton, whose restaurants dotted around the world include, incidentally, Kensington Street Social in Sydney’s Chippendale.

Bored? You can sink your Netflix account with the brand spanking new, ginormous flat-screen TV. And, for the tech titan keen to orchestrate a quick corporate takeover before takeoff, there are video conferencing capabilities in every suite (which also happen to be soundproof).

That magic button can also summon a personal shopper who will escort you to the designer boutiques in terminal five, including Bulgari, Burberry and Gucci among others.

“Some of clients can’t go up, if they went into the terminal, it would probably cause havoc,” Ms Malhotra says.

In these sorts of special circumstances, staff can also arrange for a selection of pieces to be brought to the suite for perusal and potential purchase.

How about an in-house salon?

“Most of our clients would have a beautician or stylist or people like that with them. They’re very time-precious.”

One big drawcard for visitors is the fact that VAT refunds are done in-house. (Non-UK residents can claim back 20 per cent of the cost of purchases when leaving the country.) The numerous guests who have spent millions shopping up a storm during their London sojourn, are keen to get their cash back.

“We’re talking hundreds of thousands of pounds. We’re talking bags full of VAT receipts,” Ms Malhotra says.

“You’re not going to miss out on claiming, no matter how rich you are. Travelex works with us so that your Patek Philippe watch that you’ve just spent ₤400,000 ($A700,000) on and waited a year-and-a-half for, that you’re able to claim back your VAT refund on that.”

But perhaps the biggest attraction for the rich and famous who pass through the doors is the fact there are private security and immigration services inside the building. Forget having to contend with the sweating throngs of people queuing to pass through the x-ray machines. Here, guests are privately taken through the suite’s own scanner and security apparatus.

Passports are dealt with by immigration officials who meet the VIPs in their suites.

“We don’t believe in queuing,” Ms Malhotra says. “The last thing these people want is people standing behind them, over them, around them.”

Then, just before their flights, guests are chauffeured across the tarmac in another BMW 7 series and delivered to the airbridge — and can be the first people on the flight if requested, no bumping into the hoi polloi, all impeccably choreographed.

While there are other VIP airport services at Los Angeles and Frankfurt (with Hong Kong and Singapore airports also considering introducing them), the Windsor Suites is the top dog — not too mention the most expensive and luxurious.

For many guests, once they’ve experienced this sort of pampering, they don’t go back to a regular first class lounge.

“We get to know clients very well. We can make things happen and we have standards,” Ms Malhotra says. “If you can afford it, why wouldn’t you do it?”