The 3Sixty Restaurant Group, which owns the Ego and Rocket brands, could be up for sale.
The shareholders in the business, which include chief executive James Horler and restaurant entrepreneur Luke Johnson, have appointed Coffer Corporate act as advisers regarding the future of the business.
An unidentified private equity business is thought to have made an unsolicited approach for 3Sixty, which has a total of 12 restaurants, made up of four sites under the Rocket brand and eight under the Ego brand.
James Horler said the decision to appoint Coffer Corporate came after 3Sixty sold its Mayfair restaurant in November last year for a "substantial premium" although the precise figure cannot be revealed.
The private equity business now interested in buying 3Sixty is understood to have its own management team in place and is looking for a platform for growth.
Horler added that Ego has enjoyed strong trading over the past nine months, and restaurants in central London were expected to have a strong summer. Turnover for the group currently stands at £12.7m, with site EBITDA at £1.4m. The business carries no debt.