The supermodel following the imaginary rules of Derby Day fashion

Wearing black and white for Derby Day is as traditional as proposing with a diamond engagement ring and expecting a jolly man with a white beard in a red suit to deliver gifts in December, which is surprisingly not very traditional at all.

The increasingly rigid dress code for the first day of the Melbourne Cup carnival, steering women towards outfits from the dark side and risking grass stains in white, belongs to a long line of advertising success stories.

“In 1960 there was an advertisement in The Australian Women’s Weekly calling for women to wear black and white ensembles to the races and win a prize,” says journalist Emily Power, editor of the book Fashion & Flemington. “It was sponsored by the Black & White brand of James Buchanan and Co whisky.”

Diamond giant De Beers manufactured demand for engagement rings anchored with their rocks in the forties, Coca-Cola hijacked Santa Claus, refining his image in advertisements in 1931, but it took stronger stuff to persuade racegoers in Melbourne to abandon colour on Derby Day.

“This dress is code is unique to Melbourne, and it’s not compulsory, the way that a morning suit once was for men,” Power says. “It just took off in the sixties. I think social media has reinforced it as a trend.”

Audrey Hepburn’s black and white outfit in the 1964 movie musical My Fair Lady helped the trend take hold, but up to the late nineties, women in colourful ensembles were still entering Fashions on the Field at Flemington racecourse on Derby Day. If you’re hoping to win the $78,000 prize package for Best Dressed this year, dress according to the wishes of a whisky sales team.

“I’ve always stuck to tradition,” says Fashions on the Field judge and former winner Angela Menz. “You have the rest of the week to go wild. It’s astonishing to see what people can do with black and white.”

Australian supermodel Duckie Thot is playing it safe in a white suit from designer Michael Lo Sordo, although she’s ditching the whisky in favour of Champagne as a guest in the elaborate Mumm marquee in the Birdcage.