To combat this, she has become a fan of a 200 pound-a-time treatment extracted from the eggs of Baerii sturgeon, reared on farms in the South of France. In sessions lasting up to three hours, Brad Pitt's other half is swaddled like a mummy to sweat out toxins before being smothered all over in the body cream. It promises to 'drench the skin with moisture and nourishment' and combat 'loss of firmness and slackened skin'.

Because of the high oil and protein content of caviar, it is thought to be especially moisturising. The fish smell is removed as extracts of caviar are used instead of whole roe. She has also been indulging in 90-minute facials using La Prairie's caviar-based creams.

Miss Jolie became a fan of the treatments earlier this year in Venice, after discovering them at the Hotel Cipriani's Casanova spa centre. Sir Mick Jagger, Gwyneth Paltrow, Stella McCartney and Kate Moss are also devotees of caviar facials, while Catherine Zeta Jones has been smearing the stuff on her hair to add instant gloss. The caviar-based creams are produced by extracting vitelline - or yolk sac - from the sturgeon eggs. The substance contains phospholipids, which are fats key to hydrating and softening the skin, as well as proteins said to contribute to the regeneration of skin cells.