Hipsters, Mindfulness and Brexit: the authors behind the hit Ladybird Books for Grown-Ups series on why they're quitting while they're ahead

If Peter and Jane, stars of the Ladybird books of the Sixties, were all grown up and looking for a gift for one another, they might conceivably be found chuckling nostalgically over such titles as The Ladybird Book of Mindfulness or How It Works: The Husband.

They wouldn't be alone. Since 2015, Jason Hazeley and his writing partner Joel Morris have penned 32 spoof books in the enormously popular Ladybird Books for Grown-Ups series, with more than four million copies sold and titles translated into 12 languages.

The success of their ingenious idea of matching pictures from Ladybird's archive of 13,000 images to prose that mocks the mores of modern life has not only been surprising, but also joyous. Writing their first title, The Ladybird Book of the Hipster, was, says Hazeley, "like taking our foot off the brake. We were careening downhill saying, 'Weee!'. It was just such fun".

And before long, everyone else agreed. When the first eight books were published, Hazeley and Morris were sent photos taken by friends of people in bookshops reading and laughing at their books. As gag writers on shows such as Charlie Brooker's Screenwipe, That Mitchell and Webb Look and the Paddington films, they were used to submitting jokes and not knowing how well they landed. "We're not stand-ups, we're comedy writers, so getting to see the laughs was delightful," says Hazeley.

But now, having had a lot of fun, and made a little bit of money ("Our cut after you take into account the image rights isn't huge"), they're bowing out with a bang. A hardback compendium book, The Wonderful World of Ladybird Books for Grown-Ups, will be their last, almost.

A significantly weightier book, at 224 pages, it speculates what the Books for Grown-Ups back catalogue might look like if they were to keep writing the series for years to come, with more than 337 new titles, from Mansplaining and Virtue Signalling to ­Understanding Croydon and Nature's Disappointing Animals. "This is a ­catalogue of the mistakes the publishers would have made by allowing us to continue," says Hazeley.

The pair feel they have exhausted all the most obvious subjects, leaving them with ideas that would sustain only a cover, or a few pages, not a whole book. Already though, one idea from The Wonderful World has been commissioned as a stand-alone title - The Ladybird Book of Brexit. Although Hazeley insists it's actually not that political.

They categorically refuse to write How It Works: The Teacher, even though its cover appears in the new book. "If we were to write the whole book we would be condemning every teacher to receiving multiple copies from students at the end of each year. And we're not going to do that to them. We like teachers."

Their humour, they say, always comes from a place of affection. The books are "a love letter to the Ladybird books of our childhood, which might seem like a strange thing to say when you're writing about hangovers and mid-life crises, but it works because, visually, it's a very colourful, happy, simplistic version of life," says Hazeley. "We just want people to have a giggle."

The Wonderful World of Ladybird Books for Grown-Ups by Jason Hazeley and Joel Morris (Michael Joseph) is available for £20 from books.telegraph.co.uk