Saracens condemned world champions South Africa to a third consecutive tour defeat, 24-23, on an extraordinary night for the club at Wembley Stadium.
Ex-South Africa fly-half Derick Hougaard returned to haunt the Springboks with 14 points, including the match-winning drop-goal six minutes from time.
Saracens had trailed 18-6 at the interval but hit back with tries from number eight Ernst Joubert and Brad Barritt, the Durban-born England Saxons centre.
South Africa, conquerors of the Lions in the summer and Tri-Nations champions, have now lost to Leicester, France and Saracens in the last seven days.
Saracens attracted an impressive crowd of 46,281 to Wembley, one of whom left £250,000 richer after hitting the crossbar in a half-time kicking competition.
The club may be a little poorer for it this evening — the cheque was signed by chairman Nigel Wray — but in every other way they struck gold.
Saracens are bankrolled by a South African investment company and are attempting to tap into the ex-pat community in London in order to build their supporter base.
Saracens started with seven South Africans in their side plus England international Michael Horak and Barritt, who were both born in the country. The Springboks side featured five players who played in the Lions Tests.