Leahy knows a thing or two about opulence. When the rock icon Marilyn Manson tied the knot with the burlesque queen Dita Von Teese last year, the creative hired to bring their goth-meets-Victoriana-meets-Alice in Wonderland theme to fruition was none other than this convent-educated Tipperary native, whose summer holidays were spent making cheesecakes for the family hotel in Cashel.

On a whim, at 21, she packed her suitcase and headed for New York. A Saturday job at hip boutique the Dressing Room led to her assisting the stylist Patti Wilson. “It was the best fashion education a girl could wish for,” says Leahy, who went on to work with Wilson on David LaChapelle shoots and on the iconic François Nars beauty book. Back in the UK, she learnt beading, which steered her towards the studio of Jade Jagger. “In my interview, she said she didn’t like blondes, but she’d make an exception with me — and the rest is history.”

Leahy and Jagger’s partnership took her from studio manager to assistant creative director at Garrard, where her visionary ideas injected the brand with rebellion. What other jewellery store was filling gumball machines with charm bracelets, sending fairy pendants to Kylie Minogue and trying to create a bikini line with precious stones? As art director for the Garrard parties, Leahy styled Jagger for her appearances and came up with all manner of crazy events and themes for the jewellery line. “My favourites were creating giant tattoos for Wthe windows, and throwing a party where engravers personalised the guests’ jewellery.” She also threw a “skulduggery” birthday party for Jagger a couple of years ago, with skull candles and decorations that looked so great they all got pinched.

When Von Teese performed at the Garrard store’s first anniversary, the two women hit it off. “Dita and I bonded on a shared aesthetic. I am a big fan of maximalism. If you don’t really want to make something special, why are you doing it? The whitewash approach is best kept for dental surgeries,” says Leahy.

“Bespoke — whether it’s jewellery design or putting together a party — is like, ‘Wow.’ I love the way the Regency and Victorian era really knew how to party. There was so much attention to detail. People have become lazy about entertaining. It’s all done to a formula.” Her dream theme is a Marie Antoinette banquet. “I love centrepieces dripping with flowers, berries and fruit. In those days, people would eat the table arrangements, and I love that irreverence. Marilyn and Dita were such fun to work with — they let me frame their cheesy childhood photos and put them on the walls of the castle in Tipperary.”

She commissioned monogrammed black lace panels for the windows, which now hang in the couple’s Los Angeles home. “We got carried away planning the party. I remember showing Marilyn some Cecil Beaton photographs of dyed sheep, and because we were going with black and purple goth colours, I said, ‘Yeah, we could get a sheep dip!’ But Marilyn’s transatlantic interpretation was to have an actual dip for guests to eat made out of sheep.”

Leahy’s favourite home comfort is the chaise longue she has just had upholstered in leopard print, but is considering covering in gold leather. “If you’ve got patent leather shoes, why not have a chair to match?” she says. “I think of myself as a creator of jewel-like moments, whether it’s a piece of jewellery or a great party that becomes a precious memory to be treasured.”

07958 972262, www.fionaleahy.com

How to set the scene

Times recommends

• Live chat: Thrifty ways to update your winter wardrobe
• Is anybody out there really listening?
• Nutrition Q&A: Will eating late make me fat?