Kate's dress a nod to Diana at royal baby's first outing The Duchess of Cambridge wore a cornflower blue Jenny Packham polka dot dress when she left St Mary's hospital on Tuesday. The dress was a sentimental nod to the polka dot smock her late mother-in-law Princess Diana wore after giving birth to William 31 years ago. Prince Charles and Princess Diana take their newborn son Prince William home in 1982. The Duchess looked radiant and happy in the custom made sun dress and the Duke looked handsome and proud wearing a simple blue shirt with rolled sleeves and black trousers. "The significance of this outfit is extraordinary," says Helen McCabe, Editor in Chief of the Australian Women's Weekly. It will be on the cover of hundreds of magazines and newspapers around the world - it's an image that will be seen over and over again. There will be books written about this baby, documentaries will be made and that photograph will be used for perpetuity. Charles and Diana created an a similarly iconic image when they left St Mary's hospital cradling a newborn Prince William in 1982. Diana wore polka dots on a pale green, oversized smock dress that was very fashionable in the early 80's. It's rumoured that the young princess grabbed the frock in a rush to get to the hospital during labour. Given Diana's strong sense of style it's more likely that she planned the outfit in detail. "Diana's frock was fabulous at the time but perhaps hasn't stood the test of time, " said McCabe. Kate's taken a more conservative, timeless approach. Like Diana, Kate has been universally embraced as a style icon. During her pregnancy she became the poster girl for maternity chic with many of her mum-to-be choices selling out within hours of her being snapped in them. A fan of wrap dresses, blazers, knee length coats and block colours there was much speculation about which designer the Duchess would choose to wear when she left hospital. A big supporter of British labels including Alexander McQueen, Beulah, Katherine Hooker it's little surprise she chose another of her British favourites, Jenny Packham for this historic occasion. The Duchess has worn the designer's evening gowns to many official events including the white shift coat she wore at Queen's 60th anniversary coronation in June. Stylist Josh Flinn thinks that Kate chose the perfect dress. It's pretty, classic and timeless. All the right ingredients for a history making image. Young girls will be rushing out to buy polka dot dresses this weekend. The first hint that the new parents were preparing to leave hospital was when the royal stylist, Amanda Cook Tucker, arrived at St Mary's Hospital in Paddington, shortly before Kate's parents, Carole and Michael Middleton. Mrs Cook Tucker has been cutting Prince William and Prince Harry's hair since they were children, and started styling Kate's long locks last year when she visited the Far East on a Diamond Jubilee Visit. The hair dresser arrived at the Lindo Wing with an aide, who was was carrying an infant car seat that retails for about $130, and a dress in a protective dry-cleaning sleeve. Kate reportedly has become close to Mrs Cook Tucker, who is known for her discretion and keeps a low profile. A 360-degree image outside St Mary's Hospital. Click inside to manoeuvre the photo. Image: Ben Pruchnie/Getty Images Her ex-husband, Neville Tucker, owned a Knightsbridge salon that held the Royal Warrant from 1980 to 1994. He also worked closely with the Queen's longest-serving hairdresser, Charles Martyn. Kate paired her dress with LK Bennett wedges, a cream version of the ones she wore the day after her wedding. The choice of a blue and white polka dot dress set tongues wagging in the British press about whether Kate's decision about the colour was conscious. Did she also have a pink version of the outfit hanging in a cupboard in case she was introducing a princess to the world? But the general consensus in the press was that the proud new parents got the Lindo Steps Look absolutely spot-on. with Megan Levy