"My dad, a lovely guy from an interesting, amazing family, would tell me some things but not everything," said Guest, whose American mother was a vice president of casting and talent at CBS. "Not because there were secrets, he just wasn't that forthcoming. He wasn't cold, but he didn't say everything. So psychologically, when you grow up around that, you tend not to ask questions."
He realizes that in some ways he's a chip off the old block.
"There are certain people that are open and accessible. And then there are certain people when you look at them you get the, well, I'm-not-going-over-there vibe. And frankly, I may be one of those people," said Guest, who at 65 is fit thanks to a five-times-a-week workout routine that includes cycling, tennis and an elliptical machine. "I meet people and they say this about me and I think, 'Really? That's odd.' Because internally it doesn't feel that way."
The cache of materials first led to a personal audio-recording project in which Guest conjured a family and performed all the voices. Then he thought of adding video, at which point he contacted his friend Piddock, the English actor who has appeared in several of his films.
Because of the project's open-ended nature — a young man finding his identity by creating a giant family tree — television seemed like a better option than film. There's no natural end to the series, said Guest, whose actors improvise the dialogue for every scene.
And there was no pitch to sell it either. Just a very elaborate outline with eight pages about each episode. "We said, 'That's the show,'" said Guest, who talked to several cable outlets about the project. "You know how I work, you like me or you don't."
Sue Naegle, HBO's entertainment president, told reporters this year that the premium channel "jumped" at the chance to grab it.
One of the most talked-about characters in the series is Nina Conti, who portrays Bea Chadwick, the main character's sister. She's a perfectly normal person, except she communicates through her sharp-tongued hand-puppet "Monk" much of the time. Conti, the daughter of actor Tom Conti, is actually a trained ventriloquist.
"I was having dinner with her dad years ago," said Guest, who played a ventriloquist, Señor Cosa, on "Saturday Night Live" in the mid-'80s and later in "Best in Show." "And I asked, 'How's the family?' Good. 'How's Nina?' She's a ventriloquist. 'But seriously, how is she?' She's a ventriloquist. I said OK."
The series hasn't ventured into the hallowed halls of the British Parliament, which given Guest's experiences there wouldn't be as unlikely as it may sound. When his father died, Guest inherited a seat in the House of Lords and when he was in London, which was frequent, he would sit in the chambers and listen to the voices of government.
"The people are highly educated and make amazing speeches," said Guest, who lost the seat after hereditary peers were tossed out of the august body. "They speak fluidly and fluently in English. It was very refreshing."
Did he ever speak?
"I could have made a speech, but I didn't think it was my place — well, it was my place," said Guest, who attended sessions for several years. "I thought it would be a little presumptuous of me after I'd shot all my ventriloquism scenes to stand up in the House of Lords."