Arts news with Mark Lawson. Terry Pratchett and Stephen Baxter, Your Sister's Sister reviewed, and TV writer Jed Mercurio on his new police drama The Line of Duty.

With Mark Lawson.

Terry Pratchett has teamed up with science fiction author Stephen Baxter to write The Long Earth, the first book in a projected series, which centres around a string of alternate earths accessed via a low-tech portal powered by electricity from a potato. They discuss why they decided to work together, what they argue about and who writes what.

Emily Blunt and Rosemary Dewitt star in Your Sister's Sister, a romantic comedy about love, grief and sibling rivalry. Director Lynn Shelton is known for her improvised dialogue and indie sensibility. Gaylene Gould reviews.

Jed Mercurio, writer of the TV medical dramas Cardiac Arrest and Bodies, talks about his new series Line Of Duty, which focuses on a corrupt police officer. Mercurio, who trained as a doctor, discusses the similarities and differences between TV drama's two favourite genres, and explains why the changes in modern policing make it perfect for his brand of gallows humour and unnerving realism.

Producer Dymphna Flynn.