Having shown aggressive pace in the early stages of the race, Haga attempted to sprint away, but Haslam was going with him, the Stiggy rider shadowing him for a series of laps.
Spies, meanwhile, was staying in contention, but did not seemingly pose a threat to the leading two until around five laps from the finish when he began to reel in Haslam, who could not quite find the extra speed he needed to find a gap past Haga.
When Spies did make his move, it came three laps from home as he dipped the Yamaha up the inside of turn eight. Haslam clung on though, staying alongside Spies right up to the turn ten right-hander and attempting to negate his outside line by leaving only just enough room for his rival. Spies persevered though, and was eventually rewarded with second place.
With just two laps left to catch Haga, seemingly beginning to struggle with fading tyres, Spies didn't waste any time in latching onto the Ducati, the pair heading into the final revolution nose-to-tail.
Even so, when Spies' first attempt to overtake, at the hairpin, failed to materialise, it seemed unlikely that he would relieve the experienced Haga of the win with the corners that remained. Nonetheless, Spies continued to mirror his rival, tucking in behind Haga and using his Yamaha's sheer pace to catch Haga unawares at the high-speed turn 15 and move through.
On the defence immediately, Haga couldn't respond in time before Spies was pulling a wheelie across the finish line to complete arguably the finest victory of his season.
Haga was left a rather frustrated second having shown strong pace in wrestling the lead from Spies, although Haslam was still delighted to have scored his second podium of the season for Stiggy having shown front running pace throughout.
With such intensity at the front, it was no surprise to find fourth place Tom Sykes some eight seconds behind at the finish following a very lonely race. The Yamaha rider had run with Haslam in the early stages, but couldn't maintain his pace, although the result does signal a season's best and maintains his run of top ten finishes.
The battle for fifth almost rivalled the lead for interest, with up to five riders swapping positions during the race. Eventually, Max Biaggi
prevailed after battling his way past Smrz and then Michel Fabrizio, the Italian showing decent form to eventually pull away from the battle.
After plummeting relatively quickly in the early stages, Smrz stalked his way back into contention to finish a career-best equalling sixth for Guandalini Ducati. Jonathan Rea held on to seventh, the Northern Irishman showing well in the early stages as he recovered from a poor start, while Regis Laconi
and Fabrizio – who dropped back rapidly in the closing stages – were eighth and ninth. BMW's Troy Corser
was tenth to make it five manufacturers inside the top ten.