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Tamsin Greig is probably best known for two Channel 4 roles: Fran Katzenjammer in Black Books and the constantly embarrassed surgical registrar Dr Caroline Todd in the comedy drama series Green Wing in which she starred opposite Stephen Mangan and for which she won a Royal Television Society award for Best Actress.

Other notable roles include the lovelorn Alice Chenery, in ´óÏó´«Ã½ One's comedy drama Love Soup, a role specifically written for her, and Debbie Aldridge in the long-running ´óÏó´«Ã½ Radio 4 soap opera The Archers, a part she has played since 1991. Most recently she was seen on the big screen in Tamara Drewe.

Tamsin says she found the dichotomy between the fictional and the real Matt LeBlanc fascinating: "It's almost like there are two of these people in the world – the one who is on the telly and the one you get to work with.

"The show makes a really interesting comment on the nature of celebrity, the fascination with trying to understand people's lives. It's all fabrications and falsities. This is a show that you think is about Matt LeBlanc, but at the end of the show you won't know him any more than you do now."

Beverly is, in most circumstances, a strong, self-possessed woman who doesn't suffer fools gladly: "What's great is that you see the madness of LA through English eyes, and the audience can participate and identify with our discomfort in such a weird world. Beverly is very much based on Jeffrey. He and David have this lovely idea of who they are. David describes himself as Sean; for him the glass is always half full, whereas Jeffrey just says the glass is an idiot."

Tamsin has never worked in LA: "I'm very excited about it all. It was like a great big toy box as I got each script. I've only really come to understand LA by asking other people what it is like and some of the characters are just so unbelievable and so comic they almost can't be true, but they're actually based on real people. I find it extraordinary that such people really exist!"

There were sometimes problems with language: "Yes, let's just say there were occasional problems with translation. The Americans use a different vocabulary which grates and confuses in equal measure."

David and Jeffrey admit they had never heard certain words before such as 'shambolic': "We thought the cast were just making it up. We would write the word 'totally' and they would say they would prefer to say 'rather'."

Tamsin laughs: "I had no idea what 'pussy-whipped' meant until I worked on this show!"

Unlike Beverly, Tamsin has three children: "I was interested when I read the script about how this couple have reached a certain age and don't have any children and they don't talk about that. It becomes apparent that the show is their child, so taking it to America and seeing it being changed, shafted by the system they agreed to engage with, means it's about more than just losing their art. It's about losing their sense of who they are and what they've created."

She continues: "Threesomes make for very interesting dynamics. When there are two men and a woman, people will say: 'Ah, that's interesting – the woman will be torn between the two men.' But what makes this show interesting is that there is a love affair of friendship. You know when you are in a couple and your husband gets excited about his new best mate? There's a kind of emotional love affair that goes on which is in many ways more dangerous than a sexual love affair."

She adds: "Beverly also thinks that Matt is a bit of a tw*t. He stands for everything that she finds difficult about leaving home. In fact there are lots of people she meets in LA who she doesn't really like. I think that if you take somebody out of their comfort zone, they're going to dislike people because they're not liking themselves in a situation."

Tamsin concludes: "I think what is really beautiful about these scripts is the central relationship between a couple who have been married for a long time.

"When I was growing up, I was obsessed with Cagney and Lacey. What most intrigued me was Mary-Beth and Harvey in bed in their night clothes at the end of the day, and the fact that they would talk to each other and have sex in middle age horrified me. But I was also captivated by the idea that they knew each other so well and yet found each other magnificent.

"There's something about the relationship between Sean and Beverly that David and Jeffrey have captured in these scripts that really honours the magnificence of marriage. They find each other really difficult and challenging, but they also have an ongoing and fantastic love life where they find each other brilliant and infuriating. That's captivating. It's a beautiful thing to have at the heart of the show."