Success, too, means Gervais's deadlines are his own. With his friend and co-writer Stephen Merchant, he claims the working day starts at 11.30am and finishes at 3pm, "with an hour lunch".
To one side of his desk: a framed Radio Times cover with Kate Winslet, Samuel L Jackson, Ben Stiller and the rest of the cast of Extras, the sitcom that, at its creators' insistence, was shown not as the jewel of BBC1's autumn schedule but on BBC2 over summer, yet still scooped a quarter of the available audience.
Facing him: a framed Manhattan skyline, emblematic, perhaps, of The Office's American success, the first British show to be nominated, and win twice, at the Golden Globes. In addition we might count the six Baftas, four British Comedy Awards and the programme's status as the bestselling TV DVD ever, soon to be translated into 80 languages. (Largely for this reason, an industry poll recently voted Gervais Comedy's Most Powerful Person.)
In the corner: a widescreen TV and video used, we might guess, to check the roughs of "Homer Simpson, This Is Your Wife", The Simpsons' episode he has written, or For Your Consideration, the Hollywood film by Christopher "Spinal Tap" Guest (a hero), in which he will star.
On his desk: a tidy pile of More Flanimals, his new children's book; the first entered The New York Times bestseller list at number eight.
In his lap: a draft of episode 19 of The Office: An American Workplace, the US version of The Office on which he advises. Now in its third season, it has outlasted its parent.
It's a big place, Gervais's office. But we might learn as much from what isn't here as what is. Aside from the above - desk, chair, TV, two pictures - it's a curiously bare room. Gervais sits in one corner like the boy kept behind after class. After the removal men have been in.
"Anything will distract him," says Merchant. "We used to work at his house and there were far too many things there. Do you remember Paul Daniels having a tea party with some monkeys? That's what Ricky's like. You'll be saying 'OK, we're getting on to something now' and you'll look round and he's hanging from a tyre. We've learned to strip away the distractions."
It hasn't worked. When I first meet him, he's messing around with his Apple desktop, having recently discovered internet radio. "I've found a Celtic station" he exclaims, and gives that loud, endearing laugh - Mutley chuckle rising sharply to Mad Axe Murderer - familiar to anyone who's watched the DVD outtakes of The Office, which largely consist of him in stitches, unable to finish his lines despite the fact he wrote them himself. (One scene, where Gervais's character, David Brent, gives Martin Freeman's character, Tim, an appraisal required 74 takes.)
Is he busy? "Busy in everything but the work," he says. "There's things to get ready. The [Extras] DVD is coming out. We do everything ourselves. We agonise about every detail. The fonts. We try to be more laid-back, but you just can't. You look at something and think 'That's alright. Oh, but that quote's a bit lame. Why did they put that on?'"
He produces a 2006 calendar for The Office. It's been causing him discomfort. "The BBC have wanted to do this for four years. I've finally relented, now the show's over. I couldn't stand to be seen profiting from something I'm not proud of, so it's going to charity. The body of work and the legacy are so much more important than having a top-selling calendar. It's embarrassing enough earning 1,000 times a nurse's wage for essentially showing off. I've got to earn it."
This is Gervais in interview mode. A bit earnest. He doesn't especially enjoy the process - "You can't relax until they've gone", I overhear him telling the photographer, afterwards - and he's at some pains not to be misconstrued, often doubling back on himself to argue against a point he's just brought up. It's good fun listening to him, but he's not "being funny". Fair enough: he was once asked to name three things he'd save if his house caught fire and, wittily, replied: "cat, salamander and one of the twins" only to be quizzed on the twins' names in subsequent interviews (he has no children).
And, of course, he really doesn't need to sell himself. The Hollywood A-list loved The Office; when he asked them to be in Extras, everyone he approached said yes. Since his success came relatively late in life, he's canny enough to have sussed that longevity comes through cult appeal (no matter how big that cult gets). And since that success came on his own terms, he knows the leverage he's got. "I'm a cottage industry," he says. He declined a £5m "golden handcuffs" deal: "I don't want to be the BBC's bitch". When the corporation announced, earlier this month, they'd green-lighted Extras series two, he responded "Good job... Stephen and I had already booked the studio and promised 30 actors a job." He was joking. A bit.
What sort of a comedian is Ricky Gervais? He's not a character-based satirist like Steve Coogan or a what's-the-best-biscuit? gag merchant like Alan Davies or Peter Kay. Like Larry David (another hero), Gervais revels in social clumsiness and excruciating faux pas. With insecure, infantile boss David Brent in The Office and self-serving actor Andy Millman in Extras, Gervais digs big holes for his characters, then gleefully hands them the spade. In Animals and Politics, his two stand-up shows, he upends notions of political correctness, if not quite saying the unsayable, then certainly seeing how much he can make audiences wince. He has called Stephen Hawking lazy, Gandhi annoying and made cracks about the Holocaust. One of the characters who didn't make the final cut in Meet Ricky Gervais, his unsuccessful 2000 sketch show, was called Dirty Old Queer. When he appeared on Room 101, he bucked the tradition for sending spiders and Margaret Thatcher into purgatory by nominating Children In Need.
"But I was putting a bad television show in," he says. "Why should we think that Children In Need is a good programme?"
But surely he did it for the mischief. There are plenty of bad TV shows that aren't for disadvantaged kids.
"It was a little bit naughty. But it's only that 'Is this OK?' moment. Of course you want that moment. 'Can he say that?' All these middle-class sensibilities... "
The comedian Jim Davidson recently hit the comeback trail, citing Gervais as one reason his un-PC jokes might again find favour. "Ricky Gervais gets away with gags like turning to his wheelchair-bound producer during a show, saying 'He's 31, you'd think he'd be able to walk by now,'" he said.
"Then he's got it wrong," says Gervais. "My humour isn't un-PC at all. I think it's clear there's a satirical edge to my characters, or my stand-up, even when I go under my own name. It's clearly me, getting it wrong. Playing the idiot. There's no hate involved."
'Extras' certainly ran the gamut of emotive issues. Every episode Andy Millman and his best friend, fellow actor Maggie Jacobs (Ashley Jensen) got themselves into a pickle over race or religion, or managed to insult someone with cerebral palsy or one leg shorter than the other.
"There were times when you read the script and thought 'Oh God, how am I going to get away with that?'" says Jensen, whose mother helps children with learning difficulties. "But a lot of intelligent comedy does poke you a bit. It opens things up. I don't know what they're going to do for the next series, though. Because, really, we didn't leave anyone out."
The other source of ribbing came via Extras' celebrity guests, all playing "monstrous" versions of themselves. Rumour has it that telly tough-nut Ross Kemp took umbrage at some of the lines portraying him as a wimp and Jude Law pulled out of the last episode at the last minute (the day they discover this and the subsequent failure to reach Leonardo DiCaprio's agent via a Nokia plugged into a hotel wall is captured, hilariously, on the Extras DVD). But the show that caused most consternation was one featuring Les Dennis. Suicidal, reduced to appearing in a rubbish Aladdin panto and with a dollybird fiancée who's blatantly unfaithful, Dennis's character eventually breaks down: "Why don't people want to come out and see Les Dennis? Where did it all go wrong?"
Where other actors came off as good sports for riffing on patently preposterous versions of themselves (Kate Winslet as a potty-mouthed, Oscar-eyed careerist playing a nun in Nazi Germany, for example), plenty felt that Dennis's character was rather too close to home. The actor Gerard Kelly complained, and he was in the same episode.
"But it's the press perception of him we played with," says Gervais. "Les isn't a sad, lonely man. Through no fault of his own, he became a whipping boy."
"I knew the implications of how dark it was," says Dennis. "I watched it with some friends and a couple of them had to watch a second time before they felt comfortable with it. But it was Ricky and Stephen who said 'How far can we go?' and me who said 'Go all the way'. There've been so many people who've taken the piss out of the situation I've had; to be seen to take the piss myself draws a line under it."
And anyway, Extras and The Office couldn't have built their vast audiences on provocative humour alone. In the unrequited relationship between Tim and Dawn (in the latter), and the platonic one between Andy and Maggie (in the former), there beats a big human heart.
"The Office is bigger than comedy," says Little Britain's David Walliams. "Look at the Christmas episode with the theme that David Brent is redeemed by love. That's an incredible thing to bring in. It's like the stuff Woody Allen was doing, post-Annie Hall. Little Britain doesn't have anywhere near the profundity Ricky's comedy has."
Ricky Gervais was born 44 years ago, a mistake. "My mum told me that," he says. "She went 'You was an accident'. I went 'Cheers!' Ha ha! A lot of honesty in my family." His father, Jerry, was a French-Canadian (Gervais rhymes with "raise", not "race") soldier stationed here during the war. He met Eva, the comedian's mother, during a blackout and they settled in Reading. The youngest, by some way, of four brothers, his childhood was trauma-free. Like The Waltons, he says, "If the Waltons took the piss out of each other. You had to be able to answer back." The first time he did, he got a laugh and, his family reasoned, "He'll be alright."
He could read by the age of three. At eight, he announced he was an atheist. He did biology at University College, London, before switching to philosophy (something his tutor said, "There are three things important to a good life: a decent relationship, a decent job of work and making a difference," came out of Brent's mouth, verbatim). Afterwards, he stayed on as student-union entertainment manager, for a time managing the band Suede, pre-fame. Aged 21, he was in a band himself, new romantics Seona Dancing. Their singles reached 117 and 70. The video for one, "Bitter Heart", was set in a blacksmith's.
"We'd go to the pub and buy a pint each to last all night, just to stay warm," his partner Jane Fallon, now a successful TV producer (EastEnders, Teachers) has said. "Ricky and I were the most unambitious people ever." Aged 36, he landed a job as head of speech at indie radio station XFM, and, via Fallon, was music advisor on TV's This Life. At XFM he met Merchant and they wrote together on several projects - Golden Years, The 11 o'clock Show, Meet Ricky Gervais - before their homemade Office pilot was bought by the BBC in 1999. In 2001, as he became famous, his mother died from lung cancer. His father then died the following year. (He has since done promotional work for cancer charities.)
One morning, Gervais has agreed to interview Coldplay's Chris Martin, for the music magazine Q. I go along too. The pair have met only briefly before but chatter away, with Gervais trying to persuade the singer to appear in the next series of Extras and Martin stonewalling him.
Gervais has a funny attitude to fame. Broadly, he doesn't like it. "Being famous is worse than I imagined," he says. "I don't want to be lumped in with celebrities because I use 'celebrity' as a derogatory term. I don't want to be looked at buying pants. I'm already too famous. I don't need to be this famous to be an actor or a comedian." He won't go to the pub after 8 o'clock. Too much hassle. He'd love to do Have I Got News For You and QI because he thinks they're brilliant, but really, what's the point? "I don't want to use up my cachet, the number of times my fat face is on telly."
Fame has put some peculiar offers his way. Playing the butler to George Clooney's Magnum, in a remake of Magnum, PI. Starring opposite Will Smith, as his brother. Being the singer in the re-formed Frankie Goes To Hollywood.
He's refused countless ads. When he declined one company's offer of £1m, they upped it to £2m.
Still, being in a band, casting himself in his shows - aren't these the actions of someone who's always wanted to be centre stage?
"I suppose you want the best of both worlds," he says. "You want respect and power for what you do and the best way to get that is to have a central role in something like The Office. If someone said 'You can never perform again or you can never write and direct again', that would be very difficult. Because I want it all." He concedes one aspect of fame he likes is meeting famous people he admires. "I know that if I had only written The Office, David Bowie wouldn't be calling me. He'd be calling the bloke who played David Brent."
After the Chris Martin interview has finished, Gervais gets out a video camera. He wants to film Martin for his website.
"Chris Martin from Coldplay, I've got a few questions for you. Now, you like to buy clothes in third-world sweatshops, because they're cheaper. Do you prefer Chinese or Indian-made stuff?"
"Indian," says Martin, playing along. "Chinese don't know what they're doing."
"You famously said you don't trust black people. Is that racist?"
"I think racism is a state of mind."
"On tour, you have the band and crew in stitches with your famous impression of a thalidomide. Why do they find that so funny?"
"What sort of a question is that?" asks Martin.
Where will Ricky Gervais go next? Wherever he wants. His unique position means he can turn down the offers he doesn't fancy - Mission Impossible 3 - and take up the ones he does - The Simpsons. He's working on his third stand-up show, Science. He'd like Flanimals to be a movie, but wants to take his time, avoid hype. That way, he says, it stands a chance of being the next Dr Seuss or Mr Men. He and Merchant have started on the second Extras, though they've only got as far as one side of A4. Still, Madonna and Brad Pitt both approached him at Live8 and said they'd be in it. And Tom Cruise has put his hand up, too. ("There's baggage there," he says.)
Merchant says he'd like to see them have a go at drama. "In five years' time," says Gervais, "the only place I want to be is in a room with Steve Merchant, working on a new project."
The last time I see him, he's sat behind a table in Waterstone's signing copies of More Flanimals. The shop's employees make sure everyone who joins the queue has purchased a copy of the book. Inevitably, people have snuck in other things, too. As he approaches Gervais, one young man whips out the dastardly 2006 Office calendar (all proceeds to charity).
"Where did you get that?" asks Gervais, aghast. "Is it on sale already?"
Then he catches himself and does that great big laugh.
'Extras - Series 1' is out on DVD on 31 October