That's certainly the case in his current pre-West End tour of Eugene O'Neill's masterpiece Long Day's Journey Into Night, which arrives in Glasgow next week. In O'Neill's Pulitzer Prize winning semi-autobiographical epic, the actor – best known for his small-screen portrayal of Agatha Christie's Belgian detective, Hercule Poirot – plays James Tyrone Senior, the patriarch of his dysfunctional Connecticut clan. It's a mighty role for any actor to rip into, but it's one Suchet is squaring up to as unflinchingly as anything else he's tackled.
"In my 43-year career I think this has been my most challenging role to date," Suchet says, sitting backstage in Milton Keynes. "It's the most challenging piece of writing I've ever had to perform. I compare it to being like playing Bach's organ works with everything else being like a Strauss waltz. It's that complex, but if you get it right it sings. It's very taxing. You have to throw yourself off this cliff, so there's a total disintegration of the self, and you're imploding while you do it, really."
Long Day's Journey Into Night was first seen in the UK in 1958, opening in Edinburgh with Anthony Quayle following in Fredric March's footsteps as Tyrone. While several major productions of the play have come and gone its appearances in the UK repertoire remain few and far between.
"I think audiences in some places are meeting O'Neill's play for the first time," Suchet muses. "I can't recall in my time any pre-West End tour of the play, so watching how audiences respond has proved very interesting for me. If you think of classic American plays, you think of Tennessee Williams or Arthur Miller, like Miller's All My Sons which I did in 2010. But Long Day's Journey cannot be compared with anything else in the American repertoire. It's not naturalistic. It's poetic and it's auto-biographical. People have seen Greek tragedy in there. It's huge."
Suchet's character is based on O'Neill's own father, a one-time matinee idol who became famous for his role in the Count of Monte Cristo. So associated was he with this role it effectively destroyed his remaining career.
Unlike Tyrone, however, Suchet hasn't become typecast. Long before Poirot, Suchet was a much admired stage actor who had originally wanted to be a doctor before a stint at the National Youth Theatre changed everything.
"Someone said to me that without actors, playwrights had no voice," Suchet recalls, "and I thought then, as I do now, that the performing arts are so essential to us as human beings. I thought it was a very important function for me to serve my playwrights, and to give them voice, and that's been my function all of my life since then."
Suchet began his career as an acting stage manager in Chester before travelling the country in rep. In 1973 he joined the Royal Shakespeare Company, where he more or less stayed for the next 13 years.
"That's where I really did my apprenticeship," he says, "learning about classical technique in Shakespeare, Marlowe, restoration plays, all of that."
For Suchet, a breakthrough role came playing Caliban in The Tempest. "As a young actor it helped break down emotional barriers," he says. Other roles that stand out include playing Iago opposite Ben Kingsley in Othello.
Television work followed, with portents of things to come when Suchet played Inspector Japp in Thirteen At Dinner, a big-screen Christie adaptation featuring Peter Ustinov as Poirot. The same year, Suchet took the title role of the German gardener in Blott On The Landscape, a TV adaptation of Tom Sharpe's 1975 novel concerning civic skulduggery in an English stately home.
"That changed my whole career," Suchet remembers. "I'd been doing major TV for 10 or 11 years, but Blott became a cult programme, and catapulted me into film and West End theatre. Suddenly I was known publicly, and that led directly to Poirot, which changed everything again. I was incredibly grateful that the public would accept my portrayal. You think back to all the great Poirots, like Peter Ustinov, and I was worried if my interpretation might have been boring because I literally picked him up out of the books and did him that way.
"I didn't try to be funny. Albert Finney made him very theatrical and Peter Ustinov made him a very jolly figure, so when I came along and gave him these oddities and quirks, I was frightened that wouldn't be sufficient, but thank God it worked."
This October, Suchet will begin filming the first of five new Poirot adaptations. Keeping him gainfully employed until summer 2013, these will complete the set in terms of Suchet playing the detective in every one of Christie's Poirot stories.
"That stretches over a period of 25 years," Suchet reflects.
During that quarter of a century, Suchet has appeared in Harold Pinter's production of Oleanna at the Royal Court and played Salieri in Amadeus on Broadway, both of which earned him Variety Club awards. On television, he has played Sigmund Freud, George Carman QC and Robert Maxwell, winning an Emmy for the latter. Suchet also picked up a Bafta nomination for the early noughties mini-series The Way We Live Now, and in 2004 was bestowed with an OBE.
If one piece of work sums up Suchet's balancing act between classical theatre and popular TV drama, it was probably in a TV version of Bingo, in which he played an ageing Shakespeare. It was, says Suchet of Edward Bond's play, "the most extraordinary portrait of Shakespeare".
In 2009, Suchet's own history came under the spotlight when he took part in Who Do You Think You Are?, the documentary series in which notable public figures trace their genealogy. As the son of a doctor and an actress, and the brother of newsreader John Suchet, the experience was something of an eye-opener for all concerned.
"The whole family background was terribly complex," Suchet says, "finding out that we were from Lithuanian and Russian ancestors and not French. Everything you see on screen was filmed in the moment, with me finding out these things for the first time. It was a gift."
While Suchet isn't sure if he's ready yet to play Lear or Prospero, he does express a wish to play Willy Loman, the doomed hero of Arthur Miller's Death of A Salesman. In the meantime he keeps himself on his toes by working with a drama coach in America.
"Acting styles change," he says, "and it's important to stay in touch with what's going on. If I acted the same way as when I started it would be very hammy. What drives me as an actor is an over-riding objective to get it right. If I say anything before I go on stage, it's, 'Let me get it right for O'Neill.' I'm not really interested in myself.
"I've never sought out stardom, or – that horrible word – celebrity, and everything that's become. I think as I get older and put out to grass, I might want to join a company again where I can play small parts, or big parts, or whatever's required. That way I can go on honouring the writers, because without the writers there is no theatre."
Long Day's Journey Into Night, Theatre Royal, Glasgow, March 26-31. Visit www.atgtickets.com.