Lewis Hamilton picked off one Formula One world title rival, as promised, but even he recognises the gap Sebastian Vettel has opened up at the top of the standings as "huge".

The German cruised to the 31st victory of his F1 career at yesterday's Belgian Grand Prix, with not even the protests of Greenpeace activists against the Arctic drilling plans of race sponsors Shell proving a distraction.

Red Bull's defending champion powered home 17 seconds ahead of Ferrari's Fernando Alonso and 28 in front of the Mercedes of Hamilton, despite the Englishman having been on pole for a fourth successive time. In the build-up to the race Hamilton had promised to overtake his rivals one by one to clinch the title and he did move above Kimi Raikkonen who had to retire his Lotus with brake issues.

Of Vettel's 46-point lead at the top - Hamilton trails second-placed Alonso by a further 12 - the Englishman said: "It's a big, big gap - a huge gap. It's going to be very tough to close but I'm going to keep pushing."

The race was effectively sealed after around 20 seconds when Hamilton was unable to do the one thing he knew was required on lap one: keep Vettel at bay

The getaway was clean enough, although Hamilton appeared to hit the compression of Eau Rouge hard, seemingly losing a degree of momentum and allowing Vettel to close and comfortably flash by. After that the 26-year-old was never troubled.

"There was nothing I could do," Hamilton said. "But I'm up to third in the championship, so I've done what I planned. It's difficult when he [Vettel] pulls away at the rate he does."

Even Vettel admitted his win was easier than expected. "It was a fantastic race for us," he said. "Once I passed Lewis we had incredible pace and could control the race.

"We were a bit afraid of the rain coming towards the end, but it just passed the circuit."

Alonso jumped from ninth to fifth at the start before passing Mercedes' Nico Rosberg and Jenson Button in his McLaren on laps four and five respectively and then making short work of Hamilton.