Thorbjørn Olesen edged out home favourite Francesco Molinari to win the Italian Open with a thrilling final round at Gardagolf GC.
Olesen posted a final round 64 to claim the Italian Open crown and deny Molinari a chance to win back-to-back events, but it was not without a late charge from the Italian.
Having pulled his drive a long way left on the 18th hole, Olesen suddenly found his two-shot cushion reduced to one as the home favourite holed a huge putt for birdie on the last to get to 21-under-par and put pressure on the Dane.
As his second shot found the greenside bunker it looked like there was a chance the tournament could be headed in to a play-off, but a brilliant up and down ensured Olesen's fifth European Tour title - and first since the Turkish Airlines Open in November, 2016.
Olesen had enjoyed only one top-ten finish previously this season and after capturing a fifth European Tour title said: "Unbelievable. Obviously been a little bit of a tough time for me this year.
"To come into this Rolex Series and to do what I've done is amazing, especially to come from behind and win. I haven't done that in my career so far, so that was very special.
"It was nice to hole that putt on the last and to get that feeling of holing it when it really matters.
"This is exactly what I needed. Well, it's always what we need but right now for me it's great."
One behind playing partner Slattery at the start of the day, Olesen wasted little time making his move with a birdie from 12 feet, with Molinari in the group ahead converting from ten feet on the same hole.
Birdies on the fifth and seventh kept Olesen in the upper echelons of a crowded leaderboard heading into the back nine.
Further gains from 20 feet on the 12th and tap-in distance at the next saw the 28 year old pull clear but Molinari kept himself within one by birdieing the 14th from 20 feet.
Slattery's challenge appeared to be over when he bogeyed the 14th and Molinari made light work of the par five 15th to catch Olesen at the head of the pack.
But the final pairing produced tremendous drama on the same hole. Olesen drove into trees and had to lay up with his third to 20 feet, while Slattery found the front of the green in two.
The 39 year old Englishman then drained a 30 foot eagle effort to be only one back but that margin soon doubled as Olesen followed him in for birdie.
Molinari birdied the 16th from 20 feet but gave the shot back with a bogey at the next after tangling with a greenside bunker, and when Olesen birdied the penultimate hole from eight feet it sent him two clear with one to play.
A wayward drive threw the result into doubt and when Molinari rolled in a 30 footer to huge roars from the Brescia crowd for a closing 65 a play-off looked likely, but Olesen had other ideas.
Slattery signed for a 67, with Rafa Cabrera Bello's 66 enough for fourth on 18 under. Ryder Cup vice captains Lee Westwood and Graeme McDowell rolled back the years with rounds of 63 and 64 respectively to share fifth with Andy Sullivan.