'Therapy taught me I wasn't a bad person'

She divided audiences in Sherlock, now Amanda Abbington has a new role in a West End dark comedy. She talks to Nancy Durrant about abortion, Twitter rage - and why we all need a good laugh

- Nancy Durrant

AMANDA ABBINGTON has always been terribly polite. Well, mostly. "Unless I'm in the car on A my own and people don't say thank you," she says. "Then I'm really mouthy and nasty." She's not kidding. She once got so cross on the motorway that she followed someone in her car to a service station car park to tell him off. He was mortified, and she ended up buying him a coffee because she felt so bad about it.

"That's one of the most embarrassing things I've done," she cringes. "From 'Why don't you say thank you?' to 'Have a cappuccino on me. I'm really sorry. Come and live in my house. Please have all my money."

Her terminal courtesy is one of the reasons that her latest play, about to open at the Criterion in Piccadilly Circus, hits so deliciously. Unfriend, the first play by Sherlock's Steven Moffat and directed by Abbington's co-star in that show, Mark Gatiss.

"I love working with those two," she says, "Sherlock was such an amazing thing to do, I loved being part of it. When Mark sent me this script and said Steven's written it and would you like to do it, I didn't really need to read it, I had a feeling; Mark's got impeccable taste; Steven's really clever. And then I did read it and it just made me laugh."

Stage star: Amanda Abbington and, below left, with fiancé and former stunt performer Jonathan Goodwin