Green and Black's has no plans to leave SE1 for Birmingham or shed jobs following a takeover by Cadbury's.
Green & Black's chief executive William Kendall, who is also staying, says: "Britain is embracing dark chocolate for the first time, just as we discovered wine 20 years ago."
The chocolate is derived mainly from cocoa grown by the Mayan Indians in Belize where founder Craig Sams and his wife Josephine Fairley had the idea for the firm when they sampled a chocolate drink whilst on holiday.
Sales have recently soared with Green & Black's bars and Easter eggs being available in supermarkets. Cadbury Schweppes, which has had 5% stake since 2002, paid about £20 million for the company.