Nico Rosberg set the pace in opening practice for the Belgian Grand Prix, leading Mercedes teammate Lewis Hamilton in Formula 1's return to action after the summer break.
Rosberg spent most of the morning in the garage, and only set his first time over an hour into the session. But when he did go out, the German jumped straight to P1, a position he would not leave.
The Mercedes driver outpaced Hamilton by 0.242 seconds.
Mercedes' rivals were not far from the dominant team's pace, with Daniel Ricciardo putting his Red Bull in third just 0.291 seconds off Rosberg's pace.
Kimi Raikkonen was fourth fastest for Ferrari, less than four tenths behind, and ahead of teammate Sebastian Vettel.
Daniil Kvyat completed a promising start to the weekend for Red Bull by setting the sixth quickest time, ahead of the Toro Rossos of Max Verstappen and Carlos Sainz.
Sergio Perez in the Force India and Valtteri Bottas in the Williams completed the top 10.
McLaren had a subdued session and finished down 16th and 18th with Fernando Alonso and Jenson Button.
Story of the session
Toro Rosso's Sainz was the first man to appear on the timesheets 15 minutes into the session, with teammate Max Verstappen next to set a time.
Hamilton re-established the usual order minutes later, however, putting his Mercedes on top of the times with a lap of 1:52.192, over a second faster than anyone else at the time.
The world champion, whose car sported a new-style rear wing, went faster a few laps later, setting a new benchmark with a 1:51.993, although Ricciardo also raised his pace to be some four tenths slower than the Briton.
But Hamilton raised the bar again and improved to a 1:51.340, opening the gap to over a second before the half-hour mark.
Teammate Rosberg, on the other hand, had a slow start to the session, the German not taking advantage of the extra set of tyres available for the first 30 minutes, managing just three untimed laps.
After a break, Raikkonen moved up to second place in the Ferrari, just over a tenth of a second slower than Hamilton.
But the session was red-flagged 50 minutes in when Pastor Maldonado lost control of his Lotus on the exit of Malmedy, crashing into the tyre barrier and damaging his car.
The action resumed after a few minutes were spent repairing the damaged barrier.
Rosberg finally set his first time of the day over an hour into the session, the German moving straight to first position with a 1:51.200.
The Mercedes driver bettered that moments later, going over a tenth faster.
|03||D. Ricciardo||Red Bull||1:51.373||+0.291||18|
|06||D. Kvyat||Red Bull||1:51.960||+0.878||18|
|07||M. Verstappen||Toro Rosso||1:52.158||+1.076||27|
|08||C. Sainz||Toro Rosso||1:52.421||+1.339||26|
|09||S. Perez||Force India||1:52.423||+1.341||20|
|12||N. Hulkenberg||Force India||1:52.614||+1.532||20|