The music guru popped up in Punchestown yesterday to help judge the Coast Best Dressed Ladies competition.
And with the help of stylist Lisa FitzPatrick, he chose mother-of-three Niamh Rothwell, who happens to be the wife of racehorse trainer Philip Rothwell.
"I spotted Niamh almost immediately as we were eating lunch in the pavillion, she stood out because of her headpiece initially but then I thought her whole look was very classic," said Louis.
Niamh wore a black lace Coast dress, which her husband bought for her at Christmas, and teamed it with an elegant white Hobbs jacket, a beautiful black Philip Treacy headpiece, gloves from Penneys, shoes by Bally and a handbag from Whistles.
"I'm so thrilled and genuinely shocked at winning
the overall prize today. I come to Punchestown every year, but I've never won anything in the Best Dressed competition before," she said.
Back on the track, there were few surprises though as Hurricane Fly stole the show yet again.
He delivered another devastating display under the ride of Ruby Walsh to win the Rabobank Champion Hurdle for the fourth successive year.
The nine-year-old was unsurprisingly a red-hot 1-4 favourite and had little trouble shaking off the opposition of a blinkered Rock On Ruby.
Among the crowds assessing the fillies and the fashion was Taoiseach Enda Kenny.
Organisers say that this year's event has been one of the best in years after bad weather saw extremely low attendance numbers last year.
Lisa Fitzpatrick said: "We saw some amazing style – the ladies at Punchestown always turn out in glamour, and even with the bad weather we really saw that they saved the best looks for last.
"We wanted a winner who was dressed appropriately for the turning weather, but also someone who really dressed up for Ladies Day.
"Niamh exuded that for us, and we were thrilled to give her the Coast prize."