You don't have to wait long for Richard E Grant's inner Withnail to surface. "Free to those that can afford it," he proclaims during the opening sequence of his new series, Richard E Grant's Hotel Secrets. "Very expensive to those that can't." It's a line he first delivered in character back in 1987, triumphantly flourishing the key to a crumbling cottage in Cumbria. ("We've gone on holiday by mistake!") He's resurrected it to describe some of the most opulent accommodation in the world.
Fans of black comedy Withnail and I, the film that saw Grant delivering a portrait of a dissolute actor that was equal parts drunken languor and mischievous devilment, will see shades of that same intensity in Hotel Secrets, as he cavorts like a gleeful child around LA's Chateau Marmont, or sweeps, awestruck, through Le Royal Monceau in Paris. Grant can't sit still for a moment: playing with remote-control loo seats, walking off with dining-room chairs, chomping down haute cuisine. He snuggles up to the "living art" (a model employed to lounge behind reception) at The Standard in Hollywood. He's agog as he plonks himself down at Charlie Chaplin's old table in the Beverly Hills Hotel – "It feels like the Holy Grail of where you can go as an actor". He gasps with appreciation as he surveys the view from the Ty Warner Penthouse Suite in the Four Seasons New York (at more than $40,000 a night, one of the most expensive in the world).
When we meet – appropriately enough at The Savoy in London, which also features in the series – Grant is still fizzing away, taking great gulps of still water (he's a lifelong teetotaller) before addressing the thorny question of why he's presenting a television series that focuses on the utterly unaffordable during a time of penny-pinching austerity.
"I got my head round it," he says, "by thinking that, in the middle of the Depression, Hollywood churned out Fred Astaire and Ginger Rogers fantasy movies. So I think we have an appetite for not being faced by the really grim economic stuff that we're fed on a daily basis. Having a peek into the thin-crust crème brûlée of how people live at that level is voyeuristically interesting to do."
Is the task something he relishes? "If you are hyper-curious, and you want to find out what goes on in making up a luxury hotel, it's the best job in the world, because you have the advantage of going backstage. The designers, the bellhops, concierges, receptionists, chefs, pastry chefs, cleaners, everything – you get the whole gauge of it. It's exactly the equivalent of a theatre: you've got the front-of-house show of it all, where the performance of the hotel takes place. But everything that is backstage is a world within a world, a hermetically sealed microcosm of people, dedicated to giving five-star service and pleasure."
The series is certainly escapist. The camera dwells longingly on gleaming Jacuzzis (often occupied by a fully clothed Richard E Grant) or the vast open spaces of luxury suites, on swimming pools, on tinkling fountains, on exotic – or garish – design details. Happily, just when the sheer unattainability of it all is in danger of alienating the viewer, Grant's sheer enthusiasm pulls the show onwards. He seems to have a particular affinity for his interview subjects, roaring with shared laughter or badgering them like an amiable Jeremy Paxman as the mood takes him.
Admittedly, some encounters are friendlier than others. In the first episode, racily entitled "Power and Money", he confesses to "sphincter-winking terror" when going to meet hotel mogul Donald Trump (who gives a lengthy monologue about the unhygienic tradition of shaking hands, before Grant gets him to confess that he does it anyway so that people won't hate him).
Bantering with the back-room staff is an easier task. "The bellhops at Manhattan's Palace Hotel that was run by Leona Helmsley [New York's 'Queen of Mean', who was eventually jailed in 1989 for tax evasion] in the 1980s: these guys were like something straight out of Damon Runyon. They were all coming up to retirement. They'd worked together for 35 years, and the stories that they had to tell were just a gift. And that was completely unexpected, as opposed to the sort of model-actor-waiters and staff in some of the LA hotels, for whom the job is just a stepping stone."
When it gets seriously weird, such as at the Barkley Pet Hotel and Day Spa near Los Angeles, Grant just lets it wash over him. "When I read the brief beforehand I thought, oh dear: this is Louis Theroux, freak-television stuff. But when you go into it you realise there's somebody out there who has got a lot of money and wants their dog to be given five-star treatment and to have closed-circuit television in their little kennel, so that they can see them at all times. You scoff and it's completely bonkers, but if somebody's providing that service, then why not?"
The "free to those that can afford it" line has particular resonance during a segment on Las Vegas, the Sin City of "comped" luxury hotel suites handed out by casinos to encourage high rollers. Grant's interview with Steve Cyr, an independent casino host (or, as Grant puts it, a "gambler wrangler") reveals a sort of aghast incomprehension.
"I've never gambled. As an actor, and being self-employed, I just live in terror of being in debt … I've said to people, 'as you get off the plane, why don't you just take this wad of cash and flush it down the loo?', but they land in Las Vegas going: 'How much money am I prepared to lose?' ... which is a very, very odd psychology.
"When I saw Steve and his client gambling, Steve was like a kind of circus master in the bullring, whipping the guy up. He was having a conversation with the dealer, and the people who were providing drinks, and he was encouraging this man to spend money, which wasn't his money. But he clearly got off on all that, and then got a commission."
Looking back, did he ever imagine that one day he'd be granted a free pass to all this bling? "I hoped that I could make a living as an actor. But how I've ended up doing so is beyond anything I could have ever anticipated. I thought I would be lucky if I could work regularly in the theatre, never in a city like London. So it's been beyond all expectations on my part.
"But you are prepared for it, in that from the moment you start doing movies, the level of luxury in the hotels that you stay in goes from nought to 100 miles an hour instantly. If I'd never done a movie, and I was plonked into this series, I would have been much more wide-eyed."
So what does he look for in a hotel? "Personal service. It doesn't matter how big it is or how many gold taps there are in the bathroom. It's that somebody gives you a sense that you're being personally looked after. The Four Seasons hotel in New York is absolutely brilliant at doing that."
Does he ever complain when that personal service doesn't come up to scratch? "Never. No, if I have bad service or a bad experience I just won't ever go back there."
What about tipping? "I always tip, because I was a waiter in Covent Garden and I know that that's what a waiter relies on, and unless the service has really been pants, I feel duty-bound to over-tip, or to tip generously.
"Once while I was a waiter, John Cleese came in, and I served him. The other waiters dared me to tip soup all over him and get Basil Fawlty to come vipering out of him, but I couldn't bring myself to do it. I subsequently got to know him, and told him about this. And he said yes, you would have been walloped if you'd poured half a bowl of soup into my crotch."
Grant returns to his waiting roots later in the series, when he's trained to carry a tray properly at The Savoy, a skill he masters with the aplomb you might expect from a one-time member of the "downstairs" cast of Gosford Park. He seems equally at home chatting to former Hollywood madam Heidi Fleiss. "The big challenge with her," he says, "was trying to compete with her 25 macaws, which were flying around the room, nesting in her shower, and trying to peck you."
Grant lets the viewer draw their own conclusions about the people he meets. "I kept in the back of my mind that I wanted to be able to go back to all these hotels, and to look the people in the face that I had spoken to, rather than go to the camera behind their backs and say: 'This person is an absolute Satanist'."
He pokes his nose round the grandest and greatest: The Ritz, The Goring, Waldorf Astoria, Caesar's Palace. But it's all a show, and Grant knows it. "It's what Napoleon said about a throne being only a bench covered in velvet. The bed that you slept in? Tomorrow night somebody else will be sleeping in it. That's the great egalitarian nature of staying in a hotel. No matter how ponced up it is, it's still a room for hire."
'Richard E Grant's Hotel Secrets' starts on Sky Atlantic HD at 9pm on Thursday 25 October