David Cross, the writer and director of Bliss, introduces his show...

Could you please talk us through the genesis of Bliss?

I was reading a story on the internet about a guy who had two families that didn't know about each other and who finally got caught. I remember thinking, "How can you even do that?" I started to think about it and do some research.

I found out there's a bunch of guys who get caught every year, normally when they fall ill. It was shocking how many instances there are, particularly in the UK. So I began to think this might make for a great show.

How did you develop it from there?

I pitched it as the idea of the guy who is one person in one room and another in another. That is a key element in classic farce - look at the sitcom Three's Company or Shakespeare's As You Like It.

Is it the case that this idea works so well because it is not purely comic?

Yes. I thought that the comedy part of this story would look after itself and that we should deal with the real part. I said to myself, "What if you had to write it, and it couldn't be silly?"

In this story, it is not just Andrew's life that's at stake, but numerous other people's lives as well. Some of the real-life stories I read are hair-raising. How did one man get away with it for 15 years? How would you deal with your wife's suspicion that you might be leading a double life? What does that do to you psychologically? I thought it was very juicy territory to write about.

How does Andrew get into this mess?

He's one of those guys who doesn't like confrontation. He hates it when a woman starts crying in front of him. He goes to break up with a woman, and when she doesn't take it well, he immediately backtracks. He's always trying to please people. He's not a bad person, but he's certainly not a good person, either. He's very weak and selfish. He denies he is selfish in order to justify his actions. He tells himself, "What they don't know won't hurt them." He truly believes that.

It's important to emphasise that he's not someone who says, "Dude, I've got two women waiting for me". In Bliss, his double life is not seen as an accomplishment. He does love these two women and children, but he's put himself and them in an untenable position. That's the fascinating psychology we are exploring in this show.

What were you looking for in the actor playing Andrew?

From the very beginning, I wanted to cast a comic actor in the lead because I feel very strongly comic actors are more well-rounded than dramatic actors. They can be funny and dramatic, and in my experience a lot of dramatic actors are not very good at comedy. I wanted a really strong comic actor in the lead, and that's why we went for Stephen Mangan.

What are his particular strengths?

In a word, reality. He is a very good comic actor, and he's totally believable. He can be sympathetic and manipulative, but also communicate pathos and vulnerability. That's tricky. You have to have some level of sympathy with Andrew while simultaneously saying, "What an asshole!"

Now I can't even imagine anyone other than Stephen playing Andrew. I'm blown away by what he did in the role, especially as it is such a difficult task. We were shooting a gamut of emotions every day. I'd be telling him, "Now you know about this thing, and now you don't know about this thing." It's crazy what we ask an actor to do. But Stephen rose to the challenge brilliantly.

What does Heather Graham bring to her role?

She's great. She's a real professional. She arrives very prepared and has a lot of questions because she's really thought about the character. She can do light and breezy, but can also internalise Kim's sadness. She is a terrific actor.

What are Jo Hartley's qualities?

Even before we had settled on Stephen, Jo was the first person where after her audition, I said, "OK, she's in it. That's Denise". She is just great. She's such a natural performer and is perfect in the role.

How do you hope that viewers might respond to Bliss?

I'm under no illusion that it will make the world a better place or make anyone smarter! But if it engenders discussion, that would be great. Ultimately, though, I'm interested in telling a story with believable dialogue and great acting. I hope it's the kind of show that people might binge-watch. They might think, "I need to know what happens next." But above all, I hope they are really entertained by it.