Nina Conti stars in Family Tree with her ventriloquist puppet Monk...

Hi Nina. Tell us a bit about Family Tree and where Bea fits into the Chadwick family.

On the surface it's a very ordinary London family, which probably means it's dysfunctional. It centres around Tom Chadwick, and I play his sister. He decides he's going to look into his ancestry for want of anything better to do and he starts to take an interest in an old box of belongings an aunt left him in her will.

My character is called Bea but Monk can't pronounce the letter B so he hardly ever says my name. She has been with Monkey all her life as a result of a tragic childhood incident. This incident caused her to go to a child psychologist who suggested that she take up a monkey puppet in order to express herself, and that's why I have ended up with the monkey.

What do you think makes Christopher Guest's style of working unique?

It was really fun and exciting. The first day was strange because we were filming a lunch scene and I (and Monk) felt a little bit unprepared. I didn't know how it was going to go. Despite having spoken to Monkey a lot on camera, I've never inflicted it on other people and I didn't know how that was going to go down. The first take was a really, long lunch take and afterwards Chris came in and said that he hadn't heard me speak. I hadn't said a word. So that was the first take and I was thinking, "Ok, I am going to have to speak in this because there are no lines written for me and if I don't speak then I'm not going to be in it."

After that it became really exciting - when you try something and it's accepted then it's ok and it becomes playtime. It's about having fun and making each other laugh.

Do you have freedom to say what you want?

I have tested the boundaries of that freedom a little and I would not be sure they are going to make the final cut. There have been moments when Monkey has said stuff and I've thought "that's not going in".

What is your favourite Christopher Guest moment?

I love it all, I am just an enormous fan and I always have been. I absolutely loved him when I was watching This Is Spinal Tap. I think I learnt the whole film off by heart like a real nerd - I knew it backwards. I loved him naming nuts in Waiting for Guffman, and in Best In Show, in which he becomes a ventriloquist which is before I become one - I looked at that and thought 'how weird'.

People tend to put on Woody Allen performances when they are in a Woody Allen film but I don't think people are capable of putting on a Chris Guest performance. It's a little daunting having him there, and I think "what would he do if he were in my shoes?" It would probably be a lot funnier but he's so encouraging and lovely to work with.

What is the brother and sister relationship like?

It's hard to put that into words - I have just imagined being Tom's sister and I haven't gone into it too much. Chris and Jim did give us bios to describe the characters but mine is just a paragraph and it's very funny. I don't feel like we need much of a back-story - it makes sense that Tom grew up in Ireland with his mother and I lived in London with my father so if there is any difference between us then that explains it.

How does Bea feel about Tom going off and exploring the family history?

Bea has her own problems, though she is interested to a point if he uncovers anything interesting. I get the impression she's just as disillusioned with her life as he is with his but she just doesn't quite have the motivation to do anything about it or seek elsewhere. She's got this monkey puppet that will stop her from ever achieving anything.

Do you think she's sympathetic?

Playing Bea is what my life would be like if I invited my stage act into my daily life; it's a horror show. Meeting people and him saying things and me feeling embarrassed - that is what it would be like.

Why do you think the subject of genealogy works as a comedic theme?

It's a clever idea that could be endless. My father [Tom Conti] recently had his genealogy done and it turns out he's related to Napoleon, and that is not a joke. It was in the papers and everything.

What are the central themes of the show?

I think all the characters are incredibly likable and funny and there is a pathetic side to everybody, which is endearing - you want them to be all right. What are we all ever looking for - just to feel whole and connected, it's a pretty fruitless search unless you find God or something!

What Bea's relationship with her family?

I think it's taken for granted; her dad is married to this bonkers woman, Luba - that's a funny relationship. The monkey and Luba, they could really tear each other to pieces. Luba cracks me up and it was very difficult not to laugh during filming with some of the things she comes out with. Bea feels a discomfort towards her and a jealousy which has disrupted the father/daughter relationship. I think she is probably devastated that she didn't end up growing up with her mum.

You've done so much of your stand-up with just you and the monkey - what was it like to have so many people around you?

It felt like I had been accepted and it was really nice. It was enormous fun to be around all those hilarious people and watch how it all grew.