Eddie Pepperell turned in level par to see his lead cut to one shot as the Sky Sports British Masters was set for an intriguing finish at Walton Heath Golf Club.
The home favourite entered the final day with a three-shot advantage but in tough, rainy conditions on the outskirts of London, he stayed at nine under, one clear of playing partner Alexander Björk.
The Swede made two birdies on the front nine to sit two shots ahead of England's Jordan Smith and American Julian Suri, with another Englishman in Matt Wallace at five under.
Pepperell is looking to become the season's first wire-to-wire winner as he seeks his second European Tour title after victory at the Commercial Bank Qatar Masters in February.
Björk is also looking for European Tour title number two after his triumph at the Volvo China Open.
Wallace holed a 15-footer on the first and a slightly longer putt on the second to get within three of the lead, while Pepperell did well to save par on his opener after sending his tee-shot and his second down the left.
Smith then became the first man to trim the lead as he got on the green at the par five second in two and got down in two putts for a first birdie of the day.
In the group behind Julien Guerrier went one better, holing a monster putt for eagle to get to eight under and within one of Pepperell.
The leader battled to save par again on the second, with playing partner Björk making a birdie to get to seven under where he was alongside Guerrier, who bogeyed the third.
Lucas Herbert made birdies on the second, fourth, fifth and sixth to get to six under and he was joined there by Smith who made his first bogey of the day on the fifth.
Guerrier and Suri both got in bunker trouble on the same hole, with Suri dropping a single shot and Guerrier making a double-bogey after also missing a short putt.
Björk put his tee-shot to 20 feet on the par three fifth and briefly got within one but Pepperell was inside him and made his own putt to get to ten under.
Smith took advantage of the par five sixth to get within three, while Wallace recovered from a three-putt on the fifth with a birdie on the seventh.
Suri also quickly recovered from his bogey with a birdie on the sixth but Smith dropped a shot on the seventh and the players in third were four off the lead.
Herbert dropped a shot on the tenth but quickly regained it on the par five next before giving it back on the 12th as he made a roller coaster start to the back nine after turning in 32.
Pepperell made another good par save from the sand on the sixth to stay two ahead and a Wallace bogey on the tenth meant there were only three players within four shots of the leader.
It was Björk's turn to hole a tester for par on the eighth and with Pepperell three-putting from distance on the ninth, the lead was down to one.
Herbert made a bogey on the 13th to drop to four under alongside clubhouse leader Sam Horsfield, who signed for a 69.
Guerrier made a double-bogey on the ninth after finding a horrible lie in a bunker to drop to three under alongside Lucas Bjerregaard, Gavin Green and Tom Lewis.
