Tom Lewis and Peter Hanson held the lead as the Portugal Masters reached a thrilling conclusion at Oceânico Victoria Golf Course.
As overnight leader Rafael Cabrera-Bello found water at the 12th and double bogeyed, Lewis drove the green at the 15th and two-putted for birdie.
The former amateur star, who led The Open Championship after a stunning first-round 65 at Sandwich, was five under for the day with three to play and 19 under for the week.
Swedish Ryder Cup star Hanson had four birdies and a bogey in his first 12 holes to be alongside the Walker Cup winner.
France’s Gregory Havret, England’s David Lynn (both 64) and South African George Coetzee (65) had set the clubhouse target at 18 under.
Chile’s Felipe Aguilar was alongside them with six to play - two birdies in his first three holes saw him snatch the lead early on but he proceeded to bogey two of the par fives.
The 20 year old Lewis holed a 20 foot putt at the 16th and with four birdies in five holes he was suddenly leading in only his third professional event.
A wild tee shot at the 14th cost Hanson a double bogey and as Lewis reached the green in two at the 17th and birdied, there was suddenly a three shot gap between the young Englishman and the chasing pack.