Gondola Group has sold the burger restaurant chain Byron to investment firm Hutton Collins for £100m.
The chain, founded by Tom Byng in 2007, has grown to 34 sites and is now focusing on expansion beyond London.
Byng is set to remain with the business.
The deal comes just months after the sale process was thought to have stalled, with Gondola said to have failed to convince potential buyers - thought at the time to have included TDR Capital, RIT Capital and Searchlight Capital - to part with £100m for the brand.
Gondola Group, which also owns Pizza Express, Ask and Zizzi, and is itself owned by private equity firm Cinven, had been expected to continue growing Byron itself when it emerged in June this year that the deal had stalled.
Hutton Collins' decision to buy Byron for £100m means that it is paying around £3m per site, and it is expected to try to grow the business substantially.
Harvey Smyth, chief executive of the Gondola Group, which also owns brands including Pizza Express, said: "Byron has gone from strength to strength since we launched it in 2007. Its passion and innovative approach have already positioned it as an important brand in the casual dining market, with exciting opportunities to continue to grow throughout the UK. The team at Byron have done a fantastic job and they leave The Gondola Group with our thanks and best wishes for the future."
Graham Hutton, managing partner at Hutton Collins, added: "We are delighted to be investing in such a pioneering brand. Byron has a clear road map for growth and a talented team in place to deliver it. We are excited to be working with Tom Byng and the entire Byron team, and are looking forward to bringing the Byron burger experience to many more diners across the UK. This transaction complements Hutton Collins' long experience of generating attractive investment returns in the casual dining and leisure sectors."