Roald Dahl and Michael Rosen explain the dark turn in modern writing for children.

Why are children's books darker, earthier, ruder, less 'wholesome' than they used to be? That's the subject of debate in this 1982 edition of Channel 4's literary series Book Four, which is still an enthralling watch more than four decades on.

On the face of it, the question that might seem surprising to anyone who grew up with, say, the Brothers Grimm or Heinrich Hoffman's Strewwelpeter. But there's no denying that by the late 20th century writing for children had taken a turn towards black comedy and sometimes cruel or scatological humour.

Presenter Hermione Lee cites as examples the work of Roald Dahl, the modern master of dark children's (and adult) stories, and Raymond Briggs' 1973 book Father Christmas, which found itself banned in some US states for daring to show Santa on the loo (she doesn't mention Briggs' more recent and even more gleefully disgusting Fungus the Bogeyman).

The highlight of this (too-short!) half hour show is the presence of Dahl himself, who reads from his collection Revolting Rhymes, which overturns classic fairy tales, exposing Goldilocks as a shameless thief and Little Red Riding Hood as a grasping little gangster yearning for a wolfskin coat.

Dahl expounds on his own writing processes, why so many adult writers fail when they try to write for children and why modern children demand faster-paced storytelling. He also reveals his own limits - "I would never put cruelty in a book unless it is funny".

But just as insightful is the studio debate in the second half of the programme. Lee and Dahl are joined by writers Michael Rosen and Elaine Moss, and we learn more about what modern children enjoy, the value of illustration, the joy of made-up words and the importance of details of real life - toothpaste, shoes, toilets - to young readers, whatever fantastical places the story ends up taking them to.

Book Four was made by London Weekend Television for Channel 4 and had its first outing on the new Channel's launch day, 2 November 1982. It ran until 1985.

Presenter Hermione Lee was already a respected literary critic, whose own published books included studies of Virginia Woolf, Philip Roth and Elizabeth Bowen. She later wrote a new biography of Virginia Woolf.