Can London's luxurious Ritz be just a four-star hotel?
After more than 50 years as one of America's premier hotel rating brands, Forbes Travel Guide is expanding into Europe, and has given just six London hotels a five-star rating.
The Ritz is not one of them.
Nor is the Mandarin Oriental Hyde Park, which includes a Heston Blumenthal restaurant and has hosted royalty. Both hotels have had to settle for just four stars.
But what makes a hotel worth a five-star rating?
Traditionally, ratings agencies have evaluated hotels' physical facilities. Forbes, which used to be known as the Mobil guide, says its ratings are more focused on service.
'Cared for' toilet rolls
Mystery guests are sent to stay at hotels several times a year and they then assess them against 500 criteria, most of which measure hospitality and service.
Standards include staff being "highly articulate" and avoiding "slang and excessive use of phrase fragments", the ends of toilet rolls being neatly pointed or "similarly cared for" and even a measurement of whether the traffic flow at a buffet is "convenient".
There are 17 categories of evaluation, including "graciousness" and "sense of personalized service".
Only a handful of hotels has fulfilled the five-star criteria. Shanghai has only two and New York just six.
But Mike Cascone, president and chief operating officer of Forbes Travel Guide, was keen to emphasise that London's four-star hotels have not lost out.
"The fours in London scored the strongest we've ever had in an initial market launch in the history of the business," he said, adding that there are "probably more fives to come" in the city.
Sarah Cairns, director of communications for the Mandarin Oriental, said the hotel had "narrowly missed" a five-star rating, and the hotel was "looking forward" to working towards one during the rest of the year.
The Ritz would not comment on its rating.
All about the staff
Roland Fasel, general manager of The Dorchester and 45 Park Lane, both of which have been awarded five stars by Forbes, said the "crucial" rating was down to his staff's "relentless pursuit of excellence".
And their work is becoming more and more complex, with extravagant requests becoming a daily phenomenon.
Guests have asked for private trains to be arranged for them, and some go hunting and ask for their quarry to be stuffed and put on a pedestal in time for their next visit.
A desperate husband once asked the concierge to repaint a car within 48 hours, as the colour was not to his wife's taste.
"We were able to deliver," said Mr Fasel. "The ultra-luxury business is really about delivering those individual service needs."
This level of personal attention, added Mr Fasel, had transformed London into the world's "most competitive" hotel market over the past 10 to 15 years.
Forbes' Mr Cascone agrees.
"It comes as no surprise that London's hotels and spas performed strongly," he said.
"The personalized service and attention to detail delivered at the city's top properties places them among the finest hospitality experiences in the world."
Indeed, some of London's luxury hotels appear to be recession-proof. Last year was the Dorchester Group's best year in its history.
But the rise of online rating sites such as Tripadvisor, where individual guests can comment on their experiences, means no hotel can rest on its laurels for long.
Felicity Gale from Quintessentially Travel, a bespoke luxury travel agency in London, says that star ratings are "still incredibly important" to their clients, despite other indicators such as Tripadvisor.
"Grading still has the same impact," she said.
She added that Quintessentially was "quite surprised" by some of the Forbes results.