Jennifer Saunders and Joanna Lumley return as Edina and Patsy as Absolutely Fabulous reaches the big screen.

In 1990, Jennifer Saunders and her comedy partner Dawn French were writing the scripts for the third series of their hit TV show, French and Saunders, when they came up with a sketch about a mad, 'modern' mother, an ex-hippy called Adriana - as played by Saunders - and her sad, straight-laced daughter, as played by French.

Encouraged by her husband, fellow writer and comedian Adrian Edmondson, Saunders decided to develop the idea further.

Originally broadcast on the BBC in 1992, Absolutely Fabulous, or 'Ab Fab' as it would come to be known, aired to instant acclaim. Patsy and Eddy shocked and delighted in equal measure, Saffy made our toes curl and gave the show a heart, Mother knocked us dead with her withering one liners and Bubble made us laugh out loud with her surreal inefficiency.

Now almost four years after a trio of 20th anniversary special episodes were broadcast on BBC1, Saunders' award-winning sitcom of barbed insults and fashionable excess finally saunters onto the big screen, directed by Mandie Fletcher.

Appropriate for their big screen debut, Edina Monsoon and Patsy Stone (Jennifer Saunders and Joanna Lumley) are still living the high life. But Edina is in the PR doldrums. Her client list has thinned and she continues to clash with her strait-laced daughter Saffy (Julia Sawalha), who has a 13-year-old daughter called Lola. Thankfully, Patsy is still in the media eye and her magazine is sponsoring the lavish Huki Muki Retrospective launch party. But things go tragically awry when they push Kate Moss into the Thames, and pursued by the paparazzi they are forced to flee to the French Riviera.

But Eddy's trusty secretary Bubble (Jane Horrocks) vanishes at the most inopportune moment so the despondent duo are forced to go on the run. And unfortunately, Edina's mother (June Whitfield) is also in the South of France to celebrate the birthday of her well-to-do sister, Violet (Wanda Ventham).

Saunders admits she was not without her worries about adapting the show for the big screen. 'I felt, what I'd always felt, which is that it wouldn't be enough to make a film version of the TV show, because that was just an excuse to make jokes for half an hour,' she says. 'No, the film had to be something different, something bigger. It had to be relevant. It had to be about Patsy and Eddy now and the reality of how their life would have panned out. And that reality, let's face it, was always going to be quite sad.'

Eddy has become an anomaly. 'She has always been an enthusiast for the new but, in an age of social media, everyone is onto everything before she can be,' says Saunders. 'The world has left her behind, in a way. She's become slightly irrelevant and behind the bounce. Neither she nor Patsy is savvy enough or hip enough - because they never were, let's face it - to keep up.'

The subject of aging in the modern world was something of particular interest to Saunders, herself now a grandmother of two. 'Eddy and Patsy don't know how to grow old, in the way that none of us seem to these days,' she says.

No one more so than Eddy and Patsy. 'They refuse to give up,' says Saunders. 'They can't, and won't, ever admit to being old.'

Both Saunders and Joanna Lumley retain great affection for the characters.

'They are a cartoon version of all of us,' says Saunders. 'And I think, at the end of the day, people like to laugh at themselves. Patsy and Eddy are awful, sad human beings, but they enjoy themselves hugely.'

• Absolutely Fabulous: The Movie is in cinemas tomorrow