Sebastian Vettel cruised to the 31st win of his Formula One career as not even Greenpeace protestors could throw a spanner in the works of the German's Belgian Grand Prix triumph.

As the teams worked on the cars on the grid just before the start, two paragliders from the activist group initially flew over the Spa-Francorchamps circuit, trailing a banner slamming the Arctic drilling plans of race sponsors Shell.

A second group of four men who had evaded security and scaled the main grandstand overlooking the grid then unfurled a banner from the roof that read: “ARCTIC OIL? SHELL NO”.

Once the lights went out, Vettel swept past Mercedes’ Lewis Hamilton soon after and from that moment he was never troubled in his on-song Red Bull.

Hamilton had to settle for third behind Ferrari's Fernando Alonso, who is now Vettel's closest challenger, but 46 points adrift.

Hamilton stated prior to the race he had to keep Vettel at bay down the Kemmel Straight that follows the sweep through Eau Rouge on the opening lap.

The 28-year-old comfortably held on to his fourth successive pole on the short run down to the tricky opening corner, La Source hairpin.

Hamilton, however, then appeared to hit the compression of Eau Rouge hard, seemingly losing a degree of momentum, allowing Vettel to close and comfortably flash by.

As far as Hamilton was concerned, that was it, game over in terms of trying to claim back-to-back victories for the first time in three years.

From that point on, Vettel was not troubled once as the rain race control had suggested was 60 per cent likely to arrive never materialised, nor did a safety car, which is prone to appear at this event.

There was one possibility on lap 27 as four cars into one tight corner, the Bus Stop Chicane, did not go.

It culminated in the Williams of Pastor Maldonado clipping one Force India in Adrian Sutil, before running into and taking out the second of Paul Di Resta, earning the Venezuelan a drive-through penalty.

Di Resta had started from a career-high fifth on the grid following a brilliantly-executed gamble in qualifying.

But again, in light of the recent structural changes made to the Pirelli tyres, race pace was lacking and it was unlikely Di Resta would have finished in the points even if he had taken the flag.

At that stage, with Vettel clear of Alonso, Ferrari brought in the Spaniard for a second stop in the hope race director Charlie Whiting would unleash the safety car.

Alonso had worked himself into second place, initially making up four places on the grid at the start to move up from ninth to fifth.

In the early laps Alonso passed McLaren's Jenson Button and Mercedes' Nico Rosberg to claim third, and shortly after stop one he swept down the inside of Hamilton at La Source as the Briton ran wide.

Unfortunately from Alonso’s perspective the safety car remained in the pits, ensuring the 32-year-old never came within sniffing distance of seeing the rear of Vettel’s car.

When Vettel made his second stop after 30 laps the remaining 14 were a coast to the line, and a further strengthening of his championship advantage as he finished 17 seconds ahead of Alonso and 28 up the road from Hamilton, it was that easy.

Behind Vettel and Alonso in the standings Hamilton is up to third, but 58 points adrift.

As for Lotus' Kimi Raikkonen, who came into the race 38 points down on Vettel and the German's closest challenger, the Finn is 63 behind after retiring for the first time in 39 races, stretching back to the German Grand Prix of 2009 when he was with Ferrari.

Suffering a brake issue that forced him into the pits after 26 laps, it also ended the Finn’s record-breaking run of 27 consecutive races in the points.

Behind the podium trio, Rosberg was fourth ahead of Mark Webber in his Red Bull, followed by Button, Ferrari's Felipe Massa, Romain Grosjean in his Lotus, Sutil, with Toro Rosso's Daniel Ricciardo completing the top 10.

The interviews that followed were conducted against a backdrop of boos, apparently for a Greenpeace protestor who tried to make his way on to the podium.

Despite that, a ruffled Vettel said: “It was a fantastic race for us from start to finish.

“It helped on the first lap getting a tow off Lewis through Eau Rouge. Once I passed him we could control the race.

“So a great result, with the car better than we expected going into the race which I really enjoyed a lot.

“Fortunately there was no rain, so no need for any critical calls to be made, and a comfortable afternoon for us.”

Recognising he never once had an opportunity to challenge Vettel, Alonso said: “We had to recover some places because we were not okay yesterday (during qualifying).

“We were then okay from the start, but the race was a little boring once we had second place.”

Despite failing to follow up pole with a win, Hamilton said: “We had a tough race, these guys were faster than us, but I’m happy with the result.

“When we started we felt we didn’t have as good a package as Red Bull and Ferrari. We’ll try and do what we can in Monza, but from Singapore I hope we can be strong from there.”