Private equity firm Bridgepoint has bought a majority share in Pret a Manger, including the 33% stake owned by fast food chain McDonald's.
Pret A Manger has been selling sandwiches since 1986
Pret's founders, thought to have made millions in the deal, are to reinvest a "significant" amount into the firm.
Pret had planned to auction the McDonald's-owned stake last year, but the deal collapsed over uncertainty in global financial markets.
Bridgepoint is interested in further expansion of the sandwich chain.
Pret a Manger currently has 200 shops, the majority in the UK. In 2008, the firm plans to open at least 30 new shops, including seven in New York. .
Founder Julian Metcalfe said: "Bridgepoint shares our vision, understands our culture and will support our roll-out plan globally."
Pret markets itself as an healthier, more ethically-sourced alternative to other fast-food outlets.
Bridgepoint recently bought clothing retailer Fat Face for £400m.