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Will colouring-in books become the new craze for grown-ups?

Children can spend many hours happily colouring-in pictures, taking care not to go outside the lines, turning black and white pictures into colour.

But now, grown-ups are taking up the habit too.

In France, it is reported that adult colouring-in books are now outselling cookery books.

Richard Merritt is an illustrator who has helped to create two such books. He told BBC Breakfast why he thinks it will catch on in the UK too.

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