PHOTO: Wategos House has sold in an off-market deal for $18.85 million.

The boss of fast-growing gym franchise F45 Adam Gilchrist has splashed out on a Byron Bay trophy home for $18.85 million, just weeks after Hollywood heavyweight Mark Wahlberg bought into the company.

The off-market purchase has smashed the luxury holiday spot’s long-standing record high set in 2006 by the same property when it last traded for a bullish $15.68 million.

The Wategos Beach property was sold by Danny Goldberg, the Vaucluse-based contemporary art collector and executive chairman of private equity firm Dakota Capital.