How We Met: Jennifer Saunders & Dr Tanya Byron

'I was drawing cross-sections of the bowel in my notebook. That's when we became firm friends'

Jennifer Saunders 49is a Bafta-winning comedian, best known for TV's 'Absolutely Fabulous' and her work with Dawn French. She and her husband, Adrian Edmondson, have three children and live in Devon. She stars in the BBC2 sitcom 'The Life and Times of Vivienne Vyle' .

We asked Tanya to do the French and Saunders Christmas Special in 2005 because Dawn and I had become fans of her TV show The House of Tiny Tearaways. When we were writing, we would arrive in the morning, have a coffee, and talk about it. We both thought we'd love to meet her.

We honestly didn't think she'd do it because she looked like she had too much credibility and integrity. Luckily she hadn't. So when we first met, Dawn and I were very nervous because we hadn't really written the sketch properly and now someone clever was arriving who would think we were idiots. But she was great at not being panicked by lack of material. And easy to work with, fantastic.

I have always had a fascination with psychology. I don't read books really. I read case studies so I found Tanya absolutely fascinating.

She knows how to take the piss out of me, which I respect. The first time I saw her, she was a force to be reckoned with; I was moaning about my kids, saying they treat me like a child. And she just said, "Well stop behaving like one." I love that she doesn't let you get away with stuff.

And then when she was very drunk, she pitched an idea. Normally, you'd say, "Thank you, do send it to my agent." But I read it and thought it had possibilities. The daytime chat show host, the person who starts as Ulrika Jonsson and wants to be Oprah Winfrey, was an area no one has covered. And she had written it from something that angered her. That's always a good place to start.

Tanya instinctively sees through people which is spooky when you first meet her. I was thinking, "I wonder if she thinks I'm behaving oddly?" But, of course, she's not like that. Interesting, though, when you're working, she will suddenly say, "Why has that made you angry?" And I will shout "I am not angry. Why are you saying I am angry?" She just picks up on little signals.

It makes her great to write with. When we first started writing Vivienne Vyle, we wanted it to have a different look, so we watched a lot of Woody Allen and Pedro Almodovar films. Tanya could always tell you the ending. At the start of a film, a boy would be run over and she'd say, "Does the mother commit suicide?"

The one thing we had a bad time over when we were working together was the typing. My typing frustrates her because I don't always do the same spacings, full stops or correct capital letters. And then when we finish, and the script is about to go in, Tanya wants to do a spell check. And she will put a full stop at the end of every line of dialogue. And it drives me spare. It makes my heart race just to remember it.

Dr Tanya Byron, 40, is a consultant clinical psychologist who has appeared on the TV parenting shows 'Little Angels' and 'The House of Tiny Tearaways'. She lives in north London with her husband, the actor Bruce Byron, and their two children. She co-wrote 'The Life and Times of Vivienne Vyle' with Saunders.

I don't often get anxious, but with Jennifer and Dawn, when they asked me to do their Christmas Special, I was meeting two women who we had discussed as models of female empowerment in my women's group at university. What I remember of it is that they are quite short, whereas I am quite tall, and here were these two short people coming towards me saying "Oh my gosh, its Dr Tanya Byron."

We worked together for three days and, after that, I would meet them both, but particularly Jennifer who at that time was writing the first series of Jam and Jerusalem. She had in mind for it an elderly character who might have some form of confusion, but she didn't want it to be dementia. So I sat with her one night in The Wolseley, that posh restaurant, and amid all this gorgeousness we discussed faecal impaction. Constipation in the elderly can cause confusion because of toxicity in the body. I had my notebook out and was drawing cross sections of a bowel. That was when we became firm friends.

Soon after, after a few drinks, I was sitting with Jennifer in another restaurant and said, "I've got this character I think you should play." When I went home I said to my husband: "I can't believe that I, who cannot tell a joke without sending people into a coma, have pitched an idea to Britain's most talented comedy writer."

I'd written about 40 or 50 pages about this woman, for myself, thinking it might make a novel. Jennifer then read it and said, "We should do something with this." And so we have. To be honest, when we started writing together, it took me a while to get my head past who she is and what's she's achieved. There was a lot of sitting in a room together, talking, and gradually a script emerged.

I think we see things in a similar way. We both enjoy observing people and deconstructing what they do. She writes so well about human behaviour – in a way that is funny and palatable, but also believable and often incredibly sad. She can see straight into people. In another life she might have been a psychologist.

'The Life and Times of Vivienne Vyle' starts on BBC2 at 9pm Thursday 4 October