Francorchamps (Belgium), Aug 25: Formula One defending champion Lewis Hamilton of Mercedes nabbed pole position on Saturday for the Belgian Grand Prix.The British driver once again showed his prowess in wet conditions by beating Germany's Sebastian Vettel of Ferrari, who had dominated the free practice sessions but was second-fastest in qualifying, reports Efe."It was one of the toughest qualifying sessions I can remember," Hamilton said, according to Formula One's official Twitter.Vettel stressed that "we didn't time it great, but in these conditions anything can happen. Tomorrow we have good pace for the race so I'm looking forward to that".This was Hamilton's fifth pole at the Spa Francorchamps circuit, which is to host the Belgian GP on Sunday, and adds to his record-extending 78 career starts from pole.Force India drivers Esteban Ocon of France and Sergio Perez of Mexico came third and fourth, respectively."It's fantastic! It's awesome to be in P3," Ocon said. "The guys did a fantastic job changing tyres really quickly."The third row is to be held by France's Romain Grosjean (Haas) and Finland's Kimi Raikkonen (Ferrari).Mercedes' other driver, Valtteri Bottas of Finland, came tenth but had already been handed a engine-change penalty and will start in the back on Sunday.Spanish drivers Carlos Sainz (Renault) and Fernando Alonso (McLaren) were eliminated in the first qualifying round after coming sixteenth and seventeenth, respectively.