The San Diego-based value investor sold 1.2 per cent of Sainsbury's, taking advantage of the retailer's rise in share price, decreasing its reportable interest in the company from 10.99 per cent to 9.77 per cent.
However, if Brandes fund manager Amelia Morris had waited, she could have made a further£15 million. Shares in Sainsbury's rocketed 14 per cent on news of the offer.
Reports also suggest Cinven and Texas Pacific Group were planning a rival private-equity bid to the possible approach by a CVC, Kohlberg Kravis Roberts and Blackstone-backed consortium.
However, the Transport and General Workers (T&G) union - which has 25,000 members working for Sainsbury's - has strongly opposed any private-equity takeover.
T&G national organiser for food and agriculture Brian Revell said: 'We are very concerned at the prospect of private equity taking over Sainsbury's. Private equity does not create wealth, they extract it for shareholders.'