London Welsh secured their first Aviva Premiership win when Seb Jewell converted Ed Jackson's late try to snatch a 25-24 victory over Exeter at Oxford's Kassam Stadium.
The Exiles battled all the way to overcome the Chiefs, who qualified for the Heineken Cup by finishing fifth last season.
Trailing 14-0 after 11 minutes, they hit back to finally snatch victory when a tremendous effort from their pack ended with Jackson driving over after 78 minutes to leave Jewell, who had come on for Gordon Ross six minutes earlier, a straightforward conversion.
The Exiles' earlier scores had come from a penalty try and a 70-yard interception try by left-wing Nick Scott.
Former Scotland fly-half Ross landed two penalties and a conversion.
Full-back Luke Arscott, winger Matt Jess and number eight Richard Baxter scored Exeter's tries.
Fly-half Ignacio Mieres landed three conversions with his second-half replacement Gareth Steenson kicking a penalty.