Busy Benedict Cumberbatch had to turn down the chance to be part of the Absolutely Fabulous movie.

The beloved British sitcom starring Jennifer Saunders and Joanna Lumley, which is set to hit the big screen next month (Jul16), features close to 60 celebrity cameos from the likes of Kate Moss, Jon Hamm, Cara Delevingne, Stella McCartney, and Rebel Wilson, but despite filmmakers' best efforts, the Sherlock star just couldn't commit due to his tight work schedule.

In her onset diary, published in Britain's Telegraph Magazine, Jennifer writes, "Mandie Fletcher, our director, is trying to lock down the casting of cameo roles between takes and sometimes I have to sit with her in a nice chair, eating a delicious Brie baguette, and throwing out names like Benedict Cumberbatch.

"Although Benedict Cumberbatch, it turns out, is busy for the next five and a half years..."

Saunders admits he wasn't the only star who turned her and Fletcher down, adding, "What is it with actors? We are offering tiny, tiny, tiny roles that will take up minuscule amounts of time and it’s, ‘Oh no, sorry, I’m busy doing films', or, ‘So sorry, I am going round the world with all my actor friends for the next two years', or a simple, ‘I’m dead!'"

But she's still more than happy with the starry cameos that feature in the film, especially that of supermodel Kate Moss.

Jennifer reveals she wrote a substantial part for the British beauty and sent it to her for approval before the supermodel had even signed off on the film, hoping she'd say yes. Kate is accidentally killed by Jennifer's character Edina towards the beginning of the movie.

Absolutely Fabulous: The Movie opens in the U.K. on 1 July (16).