Dani Pedrosa set the fastest lap time during Friday practice for the 2009 British Grand Prix, held in drying conditions at Donington Park.
A heavy downpour during the previous 125cc session left the track soaking wet for the start of the session, but conditions slowly improved - helped by bright sunshine during the second half of the hour.
The improvement in weather was mirrored in the lap times, which plummeted during the final 15 minutes on what was a visibly patchy surface with an ever-extending dry line.
A switch to slicks looked tempting, but the 17-rider field ultimately played safe and stuck with wets, on which Pedrosa took the top spot from Casey Stoner
on his 27th and last lap of the session.
Stoner, who only rode for 16 laps, wasn't even on track to defend his position, instead spending the final few minutes discussing set-up with his team in the Ducati Marlboro pit garage.
Double 2009 race winner Stoner, victor at Donington Park for the past two seasons, set a best lap time 0.245sec slower than US GP winner Pedrosa.
Third fastest was reigning six time MotoGP world champion and 2009 title leader Valentino Rossi, who set a best lap time 0.290sec slower than Pedrosa on the 25th of his 26 Friday laps for Fiat Yamaha.
Fourth was fellow Italian Andrea Dovizioso, completing a strong opening day for Repsol Honda with a late lap 0.442sec behind team-mate Pedrosa.
Jorge Lorenzo, who starts this weekend's tenth round 14 points behind team-mate Rossi, made occasional appearances at the top on his way to fifth (+0.478sec). Hayate's Marco Melandri, who used to live close to Donington Park, led the session with ten minutes to go, on his way to a solid sixth.