The race for the Nordea Scandinavian Masters was blown wide open when the final round got under way after torrential downpours at Bro Hof Slott near Stockholm.
Play was due to begin at 6.30am, but that was put back four hours, before a further 30 minute interuption left the leaders teeing off at 12.40pm local time.
Leaders Richard S Johnson and K J Choi were joined in the final group by Open Championship winner Louis Oosthuizen, one behind at the start of the day on nine under par after ending his third round with a bogey.
The 27 year old South African has the chance to be the first player ever to win The Open Championship and then another European Tour title seven days later.
Johnson needed only a par five on the first to jump into a two stroke lead, Choi hooking his drive out of bounds and taking seven.
Oosthuizen, meanwhile, three-putted for a six, missing from only three feet to be level with Choi and Argentina's Rafa Echenique on eight under.
Johnson had problems of his own on the second and third. With a bogey five at each of them there was a four-way tie with him, Choi, Oosthuizen and Echenique on eight under, with Belgian Nicolas Colsaerts now only one back.
And when England's James Morrison - a winner already in Madeira during his rookie campaign - chipped in from the sand for eagle at the ninth it completed an incredible front nine 30 which left him level with fellow Challenge Tour graduate Colsaerts.
Choi and Oosthuizen played the first six holes in four over and three respectively, but Johnson birdied the short fourth from three feet and after pars on the next three was one in front of Colsaerts.
Morrison bogeyed the short 11th, but then almost made another bunker shot at the 548 yard 12th. The tap-in birdie took him back to seven under and joint third with Echenique two behind.
