In 1978, British artist Eric Hill designed an interactive book about a yellow puppy for his two-year-old son, Chris.

Eric had noticed Chris kept lifting up the paper he was working on to see what was underneath and it inspired him to come up with a new format for a children’s book - lift-the-flap.

Since Where’s Spot? was published in 1980, more than 65 million copies of Spot books have been sold worldwide, in more than 60 languages.

Rachel Naylor speaks to Eric’s son, Chris Hill.

Eye-witness accounts brought to life by archive. Witness History is for those fascinated by the past. We take you to the events that have shaped our world through the eyes of the people who were there. For nine minutes every day, we take you back in time and all over the world, to examine wars, coups, scientific discoveries, cultural moments and much more. Recent episodes explore everything from the death of Adolf Hitler, the first spacewalk and the making of the movie Jaws, to celebrity tortoise Lonesome George, the Kobe earthquake and the invention of superglue. We look at the lives of some of the most famous leaders, artists, scientists and personalities in history, including: Eva Peron – Argentina’s Evita; President Ronald Reagan and his famous ‘tear down this wall’ speech; Thomas Keneally on why he wrote Schindler’s List; and Jacques Derrida, France’s ‘rock star’ philosopher. You can learn all about fascinating and surprising stories, such as the civil rights swimming protest; the disastrous D-Day rehearsal; and the death of one of the world’s oldest languages.

(Photo: Eric Hill with Spot in 1984. Credit: Ted Bath / Daily Express / Hulton Archive / Getty Images)

Episode 137 - Twenty-one rules of writing.