D&D London, formerly Conran Restaurants, has acquired Image Restaurants for an undisclosed sum.
Image owns London's The Avenue, Kensington Palace and Launceston Palace eateries.
The three restaurants finished their most recent financial year with turnover of £6.4m and £700,000 operating profit.
The buy will see Image Restaurants chief executive officer Chris Bodker join the D&D London board as non-executive director.
Bodker said: "D&D London have reshaped the way we eat out in this country and are now spreading their skills overseas. I am delighted that our restaurants are going to such a good home, one that is so professional in all aspects of the industry."
Des Gunewardena, chief executive at D&D London, said: "Kensington Place and The Avenue in particular are two of the restaurants that defined the renaissance of eating out in London in the 1990's and they continue to be popular and successful."
By Christopher Walton