The reality TV star chose a Peter Pilotto print dress (€1,390), a Boodles vintage diamond necklace (price POA) and a Boodles opal and diamond ring for the occasion.

Mackintosh is the official style ambassador for the 2014 festival, which takes place at the Curragh Racecourse in Kildare from June 27 - 29, and will form part of the judging panel to seek out the most stylish lady on Saturday June 28.

This year's Most Stylish Lady prize is worth almost €20,000 and includes a 5 star holiday to Dubai's Jumeirah Creekside Hotel, a Personal Shopping Experience to the value of €3,000 plus a champagne lunch in The Restaurant at Brown Thomas for 4 people, as well as an 18 carat gold diamond pendant from Boodles and an overnight stay at the Five Star Marker Hotel in Dublin.

Speaking about being this year’s style ambassador, Millie said: “I am a huge fan of horseracing and of course fashion so I’m encouraging all the ladies to put their best foot forward on Derby Day and showcase their unique sense of style to be in with a chance of winning this amazing prize.”

For further information about the Dubai Duty Free Irish Derby, call 045 441205 or visit