The £1m holiday will take in nearly all the Unesco world heritage sites, including, (clockwise from left): Orkney, Scotland; Petra, Jordan; and Rock Islands, Palau. Photographs: Alamy

When VeryFirstTo.com launched their £1m holiday last month, many dismissed it as a typical PR stunt. Indeed, even the company offering it never expected anyone to take them up on the offer: a two-year, luxury holiday taking in the planet's 962 Unesco world heritage sites (an intense itinerary that would mean taking in more than one site every single day for two years).

Then the phone rang.

An unnamed man from China, with an undisclosed background but apparently studying for a PHD, has signed on the dotted line and is now preparing to begin his journey next year. His trip will include visiting more than 150 countries over in two years, staying in the most luxurious hotels and flying business class.

Although the phone was hardly ringing off the hook, the company said they have another tentative booking and have received 15 enquiries.

"When we launched it, we didn't know if it would sell. Not all of our products do," says company founder Marcel Knobil, who launched Veryfirsto.com in November 2012, seemingly as a one-stop shop for those with so much money they need someone else to come up with ludicrous ways to spend it. Or, as they call it, "a haven for early adopters".

Knobil says the site now has 18,000 members and past products that have failed to find a buyer include a 267-carat black diamond nail polish for £160,000 and the chance to star in your own marriage proposal TV commercial for £135,000. Perhaps even the super-rich are aware of YouTube.

The £1m trip was billed as "the world's most expensive holiday", in the same vein as the most expensive lunch/coffee/bacon sandwich phenomenon. ("There is nothing that pushes my 'rage' button more," wrote chef Luke Mackay about a recently unveiled £1,000 coq au vin.) The holiday package also includes the almost obligatory nod to charity: in this case, a £5,000 donation to Unesco.

In the same month that VeryFirstTo.com launched, Graham Hughes, 34 from Liverpool, completed his own epic round-the-world journey on a much smaller budget. His four-year trip – all overland, with no flights – took him to every UN member state in a bid to gain a Guinness World Record (a claim which is still being processed as Hughes presents various forms of written and photographic proof).

Hughes's trip cost an estimated £27,000, which he funded through various loans and by making travel documentaries along the way. What does he think of the "world's most expensive holiday"?

"If people have got the money, travel is a better way to spend it than drugs or yachts. Visiting all these places is absolutely feasible in two years [if flying], but it will be difficult. You can't get a limo to all these sites. Surely they'll have to be some bus travel involved. And it's a shame that they are spending all their time in five-star hotels. I imagine that could be very lonely."

It is not known whether the Chinese participant will be travelling alone, although the £990,000 fee does allow him to bring a partner or companion. And he won't be able to boast that he's been to every heritage site. The small print confirms that the itinerary will only cover sites that are safe and practical to visit.

Hughes wishes the participant well on their trip, but adds: "I hope they know what they are getting into."