Gonzalo Fernandez-Castaño birdied four holes in a row to snatch the lead from Garth Mulroy as the BMW Italian Open presented by CartaSi reached a thrilling conclusion.
The Spaniard birdied the first at Royal Park I Roveri but six successive pars saw him lose ground to his South African playing partner on another day of low scoring in Turin.
However, four birdies in as many holes from the eighth propelled the five-time European Tour winner to 21 under par and a one shot lead.
Mulroy was his nearest challenger after four birdies and a solitary bogey over his first 11 holes, with Ryder Cup star Martin Kaymer third on 19 under.
The German allayed any concerns over his form ahead of the contest at Medinah in two weeks' time with eight birdies in ten holes from the fourth to roar into contention - although with five holes to play he probably needed a couple more gains to contend for the title.
The clubhouse lead was held on 18 under by England’s Gary Boyd - who had an albatross at the eighth with a six iron - while home favourite Matteo Manassero and Frenchman Gregory Bourdy were on the same mark out on the course, one ahead of Kaymer’s Ryder Cup teammate Nicolas Colsaerts.