Robert Sean Leonard is having a bad day. He is working on the London stage for the first time in more than 20 years, but he is jet-lagged and homesick for his family back in America. He has just been sent a video clip of his daughter meeting Mickey Mouse for the first time, at Disneyland yesterday. “That did me in,” the actor confesses. “I wanted to hang myself.”

Not only that, he’s not mad on his new digs. “I’m essentially living in the Sherlock Holmes Museum — I’m living on Baker Street. I don’t think I’ve heard an English accent since I got here. It’s all Russian, French, German. It’s like being on Times Square.”

Leonard takes a breath and apologises for his bad mood. You do feel for him — but then a Robert Sean Leonard full of the joys wouldn’t be quite right, either. His second most famous character, Neil Perry in the 1989 film Dead Poets Society, killed himself when he was not allowed to indulge his love of the theatre by a ­disciplinarian father. And his most famous character, Dr Wilson in the hit television series House, was last seen riding off into the sunset (literally, and on a motorbike), alongside Hugh Laurie’s cranky doc, to die of cancer.

So, personally, I would be disappointed to find him overly chipper, even though his latest stage role is a peach: Atticus Finch, the hero of Harper Lee’s 1961 novel To Kill a Mockingbird, about a lawyer standing up to racism in the Deep South. This is Leonard’s first time in London since filming Kenneth Branagh’s Much Ado About Nothing in 1992, so it is hardly surprising to find him a little bit perturbed by his surroundings. For eight years (2004-12), he was the only irreplaceable supporting character in arguably the biggest TV series in the world. To these eyes, at least, it was his two-handers with Laurie’s Dr Gregory House that raised the show above cut-and-paste hospital drama.

The broad graph of Leonard’s career has been bursts of screen fame set against sustained, tranquil success in the theatre. Every screen actor loves to talk about how they yearn for the boards, but Leonard has spent the bulk of his 44 years treading them. After the release of Dead Poets Society, in which Leonard and Ethan Hawke (a lifelong friend) were essentially co-leads, Leonard steadfastly ignored that film’s advice — “carpe diem” —and instead did a small play in Philadelphia. These days, if a 20-year-old actor starred in a $235m movie, he would find himself on what Leonard describes as a “conveyor belt”, whisked away by publicists and agents, and fed into the Hollywood system.

“No one put us on that conveyor belt,” he says. “We didn’t even get publicists when that movie came out — and I’ll make it perfectly clear, I think that’s absolutely the best thing that could have happened to us, maybe even as actors as well, but certainly as people. We were in New York, strumming our guitars and making friends and doing off-Broadway plays. I don’t think I had even been to LA. It was a wonderful time.”

Instead of blasting off into the movie stratosphere, Leonard began amassing Tony nominations for work on Broadway, including a long run as the go-to man for American productions of Tom Stoppard’s plays — he eventually won his Tony for The Invention of Love in 2003.

Yet when he is recognised in London or his native New York, it’s not for his stage work, and these days it’s rarely for Dead Poets Society. It’s for Dr James Wilson in House. The original idea behind the series was to take Sherlock Holmes and put him in a hospital: a master detective, but on the trail of disease and diagnosis. Wilson was House/Holmes’s Watson, his one true friend in a world of mediocre minds that House regarded with disdain.

Meeting Leonard, it’s hard to square how this dyed-in-the-wool theatre man — diffident bordering on nervy, even now — wound up in a hospital drama at all, let alone as a linchpin of one of the biggest shows of the past decade. Leonard is brutally frank about his experience: he loved Hugh Laurie (“We could talk about Peter Cook, we could talk about Alec Guinness”), they made a good pair — but to Leonard, House was mostly about the money.

“I wouldn’t be here with you now if it wasn’t for that. Getting my family over here and back is going to cost more than I make in the whole run of To Kill a Mockingbird! You can’t do theatre jobs like this unless you have money.”

As a dedicated House fan, it is mildly deflating to learn that the actor who gave you all that pleasure took so little pleasure out of the endeavour himself. “Listen, I think the show was good, I was proud of it, I loved Hugh, I didn’t have any scandalous problems. I just didn’t really enjoy it, which no one wants to hear.

“It was tough. I had to get up at 3.30am every day because I lived an hour and 20 minutes from LA, and our call was 6am. Then it was 15- or 16-hour days. You’re braindead the whole time you are working, you have no time for family and you don’t read your daughter stories at night. That’s what they were paying for in my case.

“But I’m so glad I did it — we knew we wanted to have kids, and we had no money. I thought, ‘Well, shit, college is $60,000 a year. What are we doing? I can’t keep doing Tom Stoppard pieces, it’s ridiculous.’”

That is the stark reality of being an actor. With House done, now Leonard can keep doing Stoppard, should he so choose. But first there’s Atticus Finch to get out of the way.

“My friend said, ‘So you’re wrestling the ghost of Gregory Peck for 1,200 people, eight times a week. And you thought that was a good idea?’ He’s right, I’m not going to win that. I mean, I would pick Gregory Peck over me — and I’m me.”

Leonard, as this suggests, is self-deprecating to a fault. He spends a good quarter of an hour trying to convince me that “almost everyone” is a better actor on film than he is. Then I tee him up for some choice anecdotes of times spent with Laurie, to which he responds by saying that, actually, they’re not that good friends at all.

“A lot of kids at my daughter’s school ask me, ‘Do you live with Hugh Laurie?’ I just say, ‘Yes. Yes, I do! Tell all your friends.’ No, I haven’t phoned up Hugh here, I haven’t talked to Hugh in a while, and I don’t know what he’s doing. He was going to do some pirate film, and he didn’t — which I was glad about, because I’d said to him, ‘I don’t want to explain to my friends you on the side of a bus with a parrot on your shoulder.’”

It is all a long way from ‘O Captain, my Captain’, gadding about with the Peter’s Friends mob on Much Ado About Nothing and thinking theatre could change the world.

“When I first came here to London, I was a kid. I went out every night and I felt like a rock star. Again, I mention Ethan Hawke because he’s a big part of my life — we were talking about how he used to call me at two in the morning, and he’d say, ‘Oh I’ve just had this idea, we should do a film of Romeo and Juliet, but instead of you playing Romeo, I think I should play Romeo and you should play Mercutio...’

“It felt like we were planning D-day. It felt so important which one of us would play Mercutio! Looking back on it, I think, ‘Who gives a shit?’ You think what you do — your art, this play or that play — you think it’s so important. It’s not unimportant, but it’s not heart surgery.

“So now I feel lucky to work in a beautiful place with people I really enjoy being with in the simplest way. What I had then was excitement and newness and exploration. Right now, I want to watch my daughter meet Mickey Mouse.”

Ok, so last night I went to see the play.
The theatre itself is amazing, this big arena like greeks theatre in the middle of the park (and I'm sure it must be lovely in summer). We arrived a little bit late and we had to wait to be seated...it took about 20 minutes and there was no trace of RSL and we were getting a little scared...then we sat down (not the seats we had booked, we lost them by arriving late) and then from the stands arrived Robert, aka Atticus Finch! I think he did a great job and really nailed the souhen accent, an essential part of the charqctrr, and Atticus...I feel in terms of morality he has a lot in common with Wilson. On a funny note, I.coulndt help but giggle everytime he said House! My favorite part were his interacion with the kids actors and the final.statement of the trial: he rolled up.the sleves of his shirt and went for it, really touching, the voice cracking with emotion.
All acotrs did a great job, the kids were amazing and it is not an easy text for young children. The arrangement was original: at the beginning there's just the stage, empty and blank
, then as they read he play acotrs stqrt o build up the sfene, drawing with chalcks on the stage, bringig furniture...I mean, really enjoyable, and there is a guy with a guitqr playing and singingi durine the pauses, people reading out loud from the book the charqcrer's inner thougts...it was like a.symphony, and for me having missed going to the theatre for months it felt special.
One thing left me puzzled: at the end of the play actors luned up and took.he applause but just once, they left the stage and didn't coke back, while the audience was rushing to leave...I guess it was too cold for everybody, still...
We did try to.wait, we actually found the actor's entrwnce and ahahahah through a window ee actually saw RSL hface! We waited a bit, but it was getting late and we had to.catch the tube. Overall a great night, ai hope the weather will keep up brcause this play , not just for RSaL, deserved to be seen.
And it made me want to read the novel: tthere eere some witty lines there, and there are characters I would like to get to "know"better.

Thought RSL was terrific, put so much pathos and feeling into the role. Also impressed with actor who played Tom Robinson, brought tears to the eyes with his scene in the witness chair. Thought the little girl who played Scout last night was good too, got the timing right with the humorous lines those playing The boys less good, not yet comfortable in the roles. The reading of passages from the book throughout the play was unusual, but actually was quite good, especially if one hadn't ever read the book (like me) or had never seen the film. One thing that struck me very much about RSL - am beginning to wonder if he actually has something wrong with his arm (someone may actually know). As Wilson he tended to play quite a lot of scenes with one hand in his pocket. He did the same as Atticus. It may be pure coincidence, or simply habit, but it did get me wondering - not that I am implying that the reason is anywhere near the same as the reason Michael J Fox did it, don't think that is the case at all, at least hope not! Interesting venue, which I had never visited before - its prob about 40 years since I was last in Regents Park! Overall thought it was great, had no problem joining in the standing ovation and was worth getting absolutely freezing cold for, and the long tiring walk back to the Tube (bearing in mind I have no night vision and have to rely on my minder to guide me through the dark streets), and being exhausted when I got back home at 1.00 am. At least the man upstairs answered my Prayerrs, and it didn't rain.