The ad was directed by Jake Scott, son of director Ridley Scott, and stars actress/model Alyssa Sutherland, who appeared in last year's 'The Devil Wears Prada'.
The new multimillion-pound advertising campaign for Flake represents the largest spend by the brand in the last five years.
The ad features rain drops falling upwards and water droplets running backwards across sensual shots of calves, a cleavage and a pair of uncovered thighs -- all backed by a reworking of the familiar tune.
The ad, which will also run in cinemas, was created by Publicis and has the actress eating a flake in a convertible car as she gets soaked in rain. Eventually, the rain stops and the sun comes out, basking Sutherland in a warm glow.
The Flake bar was first introduced not long after the First World War in 1920. The first Flake ad aired in 1959 and the brand's advertising was recently voted the "nation's favourite" by ITV viewers on 'Best Ever Ads 2', broadcast on June 17 2006.
Tony Bilsborough, a Cadbury spokesman, said: "The Flake girl is so well loved by the British public that it made sense to bring her back. While we can't reveal any more details at this stage, we are confident that the new campaign will be one of the most talked-about ads of the year."
The iconic theme tune, which goes "Only the crumbliest, flakiest chocolate, tastes like chocolate never tasted before", was written by Ronnie Bond, one of the most prolific and successful jingle writers, who was also responsible for Kellogg's Bran Flakes "Tasty, tasty, very very tasty" and KwikFit's "You can't get better than a Kwikfit fitter".