Simon Callow is a proper one-man show. He acts, he writes, he plays music, he directs. He could do a one-man show about himself, if he weren't busy doing one-man shows about others.
He has "done" Dickens and Shakespeare and now he is Inside Wagner's Head.
Simon also has a tendency to be one-question interviewee. Start him off and there is no stopping him.
Asked to explain his interest in the composer of the Ring of the Nibelung and the rest, and he's back at the dawn of the 20th century and examining his grandmother's own fascination with the great German.
"She was a singer, although more of a fan of his orchestral music," he says. "I heard all that when I was a boy. When I first went to see the Ring cycle I was overwhelmed. After that I went to see a Wagner opera whenever I could.
"I had all the recordings and read pretty well all the books. This all came to a peak about three years ago when I went to Bayreuth Festival and saw three operas. I became interested in the man and his place in German history and culture."
Which is the heavily edited version.
He read even more "from every angle" when was commissioned by the Royal Opera House to "do something" about Wagner.
"But I didn't know what," he says, showing an actor's skill in not apparently taking a breath. "I told them that and just talked about him for an hour and a half and stopped."
"They said, 'that's the show'. So it is my response to him."
Response being a key word. Wagner's association with Nazi Germany colours many views on the composer and his music.
"Hitler adopted Wagner but there is nothing Nazi about his music," says Simon. "The Ring is about the collapse of capitalism and authority and the move towards an anarchic way of living, not Nazi at all. He was a radical and an anarchist.
"He was, though, deeply anti-Semitic."
That has made it "intolerable" for Israel to accept Wagner's music.
Judging art by the artist is wrong, Simon believes. "If he were a serial murderer he would still have been a very great artist.
"Where does that start and end? Even Enid Blyton was not much of a sweetie."
Simon is more luvvie than sweetie. There's a theatrical performance about the man and his speech as if he always performing. And yet none of it feels like an affectation. That naturalistic and genuine air has made Simon one of Britain's most accomplished and popular actors who is at home in "literate" or light film (A Room With A View, Four Weddings And A Funeral), heavyweight drama or farce on stage, or anything at all on telly (most recently The Labours of Hercules, David Suchet's last Poirot).
His writing stands out, too: including a superb autobiography and his current project, the final volume of a three-part biography of Orson Welles.
You will see him next year in Americus, a big-budget film about Italian explorer Amerigo Vespucci.
Simon is also one of the most influential gay men in Britain and was one of the first actors to come out (in 1984).
As a viewer this week, he was captivated by Tom Daley's revelatory video, about dating a man.
"It was wonderful and wonderfully done," he says.
"It is greatly symbolic for many, many young people."
Tom is clearly rather too young for a Simon show, not that the actor and writer is seeking a fresh subject.
"They take up so much time to research and write," he says.
Instead he is still in tune with Wagner. "People who think his music is bombastic, which some of it was, would be surprised if they listened to more. He composed the most tender and delicate music, with such a sense of nature."
Singular, then, rather like Simon.
Inside Wagner's Head is at the Theatre Royal Plymouth from Thursday to Saturday next week.