A busy mum sits at a table surrounded by crayons, colouring in a child's book, taking care to stay within the printed lines and fully concentrating on the task.

There's nothing unusual about that, you might think, except there's not a child in sight...and the mum is simply colouring in because she wants to.

Grown ups reaching for the crayons is a new global trend it seems, as adults say they're attracted to the creativity that colouring in affords.

Scottish illustrator Johanna Basford has sold more than 1.4million copies of her colouring-in book for grown-ups, Secret Garden. The follow-up, Enchanted Forest, is expected to do just as well

Art and flowers: The book is the most popular in its genre and has now been translated into 22 languages

If you needed any proof, then browsing Amazon's bestseller list offers it.

A book called Secret Garden by Scottish illustrator Johanna Basford, which includes 96 pages of black-and-white drawings has sold more than 1.4million copies and is riding high in the bestsellers chart. So far, it's been translated into 22 different languages.

The New York Times has even reported on 'colouring-in groups', where grown-ups meet, as if they were in a knitting circle or book club, just to neatly daub colour on the right side of lines together.

The arty fad is said to have started in France, where it was promoted as both a therapeutic hobby and a way of rediscovering lost creativity.

Adult colouring-in titles are now said to be outselling cook books in the country, no mean feat for a destination that holds gastronomy so close to its heart.

The allure is said to be the unadulterated pleasure of doing something for no purpose other than to enjoy the practice of colouring and staying within the lines.

According to experts, it's a kickback against the stresses of modern life and technology, where everything, even leisure time has to be in some way useful or aspirational.

The images in Basford's book are not particularly adult in theme, they depict scenes of both nature and fantasy.

Basford, 31, told The Times: 'Colouring in appeals to people because it’s a chance to do an analogue activity that’s not on a screen. Everyone is creative deep down but as you get older you get less confident in your abilities.'

The artist's second book, Enchanted Forest, is showing all signs of eclipsing the success of her first work.

Basford says her success is down to people resisting modern technology in their leisure time. She says: 'Colouring in appeals to people because it’s a chance to do an analogue activity that’s not on a screen'

In Australia, colouring-in circles have emerged, such is the pursuit's current popularity.

One crayon fantatic Jenny Keane told the Sydney Morning Herald that she even enjoys colouring in with her husband: 'During the week some people like to go to the bar to decompress, whereas my husband and I like to sit down together and just colour.'

She adds: 'I can't draw but I like to use my hands to get creative. Some people might use yoga or running but colouring for me is my sense of peace.'