Calveton and Breal Capital are to acquire the group with the deal expected to be signed this week.
David Loewi, D&D's chief executive and co-founder, says he is 'absolutely delighted' to welcome Calveton and Breal Capital into the D&D London family.
"This partnership will provide us with the financial backing and strategic support to accelerate growth both in the UK and internationally,” he adds.
The deal will see both Calveton and Breal invest proprietary capital 'patient' money, unlike institutionally backed private equity funds with exit time horizons.
"D&D London's reputation for quality food and creating memorable experiences is unparalleled," says Sandeep Vyas, founder of Calveton, which also owns burger chain Byron.
"We see immense potential in this partnership and are excited about the business growth ambitions, which we will support wholly as partners. Our shared vision is to preserve the rich heritage and identities of these remarkable restaurants.”
In the last year, D&D London has closed seven smaller, uneconomic sites, including its Avenue, Radici and Plateau restaurants in the capital, as well as East 59th in Leeds and Klosterhaus in Bristol.
However, it still operates around 40 restaurants and bars, with one hotel based in London.
The group hopes to expand in Manchester, Leeds, Paris and New York, and has a projected turnover next year of £144m.
Founded out of Conran Restaurants, D&D’s restaurants include Coq d’Argent in the City, Quaglino’s brasserie in St James’s and Bluebird in Chelsea.
The investment from Calveton and Breal would result in a '£40m balance sheet recapitalisation', which the group says will give it 'a clear runway for continued success and further growth'.
"We have always been selective in the opportunities we pursue and recognise that D&D London is a true gem in the world of hospitality," says Brent Osborne, founder of Breal, which has also recently acquired Vinoteca, Black Sheep Brewery and Brew by Numbers.
"We are pleased to be part of this exciting journey and look forward to working closely with David Loewi and the talented team at D&D London to build on their impressive legacy. This acquisition represents a great platform upon which the various restaurants and bars within the group can be taken forward in partnership, delivering long-term sustainable growth."
Existing shareholders Beechbrook Capital and D&D management will be selling down to its new shareholders, but will remain as investors, with HSBC and Santander continuing to provide debt.
Simon Wilkinson, former boss of Byron and La Tasca, will join the D&D board as chief advancement officer.