London - A colouring book has become a sell-out success thanks to an unusual twist – it is designed for adults.

Since British artist Johanna Basford created one of the first colouring books for grown-ups in 2013, called Secret Garden, it has sold over 1.5 million copies and inspired a flurry of similar books.

Now, the 32-year-old’s second book Enchanted Forest has sold out within weeks of its release. About 226 000 copies were scooped up last month and the publishers have now printed another 250 000.

Enchanted Forest reached number one on the UK Amazon book chart at the start of April, while the two books took first and second place on Amazon’s bestsellers list for the US.

Mother-of-one Basford, from Aberdeen, said she has been contacted by people from all walks of life who enjoy her “stress-relieving” books, from artists to investment bankers. She added: “I think it has been a bit of an underground movement for a long time.

“People have always loved colouring because it is a very accessible way of unleashing your creative side. But I think it was seen as childish. By creating adult books, with more intricate designs, it makes it more socially acceptable.”