"It's only in acting where the word 'improvised', or a lack of preparedness is seen as a good thing," says Alison Graham

"Mercifully, I haven't been type-cast and it opened more doors than it closed. I was never bored, but I wanted to make sure I left before it became a job."

See the two former Doctor Who stars in the trailer for BBC1's new improvised series about intertwining relationships