An impressive Lewis Hamilton lay down the title gauntlet to Sebastian Vettel after soaring to the top of the time sheets in second practice for the Belgian Grand Prix.
Hamilton, who will take part in his 200th race on Sunday as Formula One returns to action following its summer hiatus, finished 0.262 seconds clear of Ferrari's Kimi Raikkonen, while Vettel was only fifth.
The fast-sweeping nature of this famous Spa-Francorchamps circuit is expected to suit Hamilton's Mercedes team, and on the evidence of practice, the Briton will be in prime position to get his stuttering championship assault back on track on Sunday.
Hamilton, also bidding to match Michael Schumacher's all-time pole record of 68 in qualifying tomorrow, was fastest in second practice, and probably would have been quickest in the opening session, too, had he bolted on a set of the speedy ultrasoft Pirelli tyres.
But the 32-year-old Briton will nevertheless be pleased with his form as he seeks to overturn a 14-point deficit to Vettel with nine rounds of this see-saw championship remaining.
For Hamilton's chief protagonist Vettel, it could be about damage limitation this weekend. His Ferrari car has so far been suited to the slower, twisty tracks, and the layout of this famous circuit deep in the Ardennes is anything but.
Indeed Vettel was nearly half-a-second adrift of Hamilton in second practice with Valtteri Bottas third, and the Red Bull of Max Verstappen fourth.
Rain threatened to hit the second practice session on Friday afternoon, and so it arrived under ever-increasing dark clouds with 30 minutes remaining.
Daniel Ricciardo and Fernando Alonso were among those brave enough to take to the track, but both were soon back in their respective garages with the threat of sustaining damage too high in the tricky conditions.
Britain's Jolyon Palmer, who scaled Mount Kilimanjaro during the summer break, is bidding to get his grand prix career back on track.
Palmer is one of only two drivers yet to score a point this term, but the Englishman will be heartened by his lap which was good enough for 10th place before the rain struck. Alonso finished 11th for McLaren, two places ahead of his team-mate and home favourite Stoffel Vandoorne.
Felipe Massa, who missed the last round in Hungary through illness, failed to complete a single lap on Friday after he crashed out of this morning's session.
Massa, 36, lost control of his Williams through the right-handed Malmedy before running off into the gravel and into the barriers.
The former Ferrari driver walked away from the incident unscathed, but his Williams team were unable to get his car ready in time.