With the Cannes Film Festival in full flow, I have decided to dedicate today’s fashion post to the style of the French Riviera, the effortless, glamorous looks that first came to prominence with Brigitte Bardot in the 1950s, and have then been embraced by every style icon since, from Jane Birkin and Audrey Hepburn to Diane Kruger and Michelle Williams. Breton stripes, straw hats, classic white cottons and gingham peddle pushers, Riviera style has been a classic look that has little changed since the days of Brigitte and Audrey Hepburn.But this season, Topshop has decided to put its own spin on Cannes style staples and have created a collection that…