It was the third stage win on the Tour for Belgium"s sportsman of the year, though by far the sweetest. After the third stage, Boonen had marked out victory in Balen as a main objective.
An unimpressive attack by the septet of Nicolas Portal, Mathew Hayman, Bert Roesems, Sebastien Portal, Michiel Elijzen, Thomas Lovkist and Koen Barbé that never counted upon an advantage of over three minutes was swallowed up with ten kilometres remaining, as rain began to lash down heavily upon the riders.
The pace of the peloton, driven by Quickstep and Milram was too great for any late attacks to succeed in the way Manuel Quinziato did on stage 2.
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The Quickstep plan once again worked to perfection over the final few kilometres. Bram Tankink led the field until 1000 metres to go, before peeling away for Wouter Weylandt to launch the sprint.
As Boonen sat comfortably on his wheel, Simone Cadamuro tried to attack from a long way out, but the home favourite was not to be denied. He powered away as Cadamuro faded, and punched the air as he crossed the line to the screams of a jubilant crowd.
"This is a very special moment for me. This win means as much as my success in the Tour of Flanders," Boonen said. "I'll remember for ever how the fans by the side of the road welcomed me when we arrived here.
"Everybody expected me to win again today. But it was far from being easy. I feared a fall or suffering a puncture and the rain made things even worse on the second part of the stage," he ad ded.
A late surge from Julian Dean saw him take second, with Cadamuro back in third and Baden Cooke fourth.
Discovery Channel's George Hincapie finished safely in the pack and retained the leader's claret jersey.
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