Belgian GP: Mercedes' Rosberg fastest in FP1 with halo fitted

The Mercedes driver clocked a 1m48.348s on the super-soft tyres while evaluating the halo, to finish 0.730s clear of team-mate Lewis Hamilton, who was on the same tyres.

Reigning world champion Hamilton was running a fresh power unit, which featured the use of a sixth MGU-H and turbo that currently results in a 15-place grid penalty at Spa.

Ferrari's Kimi Raikkonen, on the soft rubber, was Mercedes's closest rival, 0.799s off the pace with Sergio Perez just over a tenth further back for Force India.

Three teams - Mercedes, Force India and Toro Rosso - ran the halo for the first time when they bolted the device onto Rosberg, Nico Hulkenberg and Carlos Sainz Jr's cars respectively.

Red Bull fitted it for the second time, after Pierre Gasly tested it in the Silverstone test, with Daniel Ricciardo carrying out the testing duties and completing a single installation lap with the device.

Rosberg kept the halo on for two runs before removing it and switching his attention to the team's weekend programme.

Sebastian Vettel was fifth, 1.420s slower than Rosberg, ahead of Ricciardo, Max Verstappen and Hulkenberg.

Valtteri Bottas and Esteban Gutierrez completed the top 10.

Sauber appeared to have made a step forward with its new aero package, which features a new front wing, short nose, floor and front and rear brake ducts, with Marcus Ericsson 13th.

However, the Swede has taken a sixth turbocharger and will therefore take a 10-place grid penalty for Sunday's race.

Esteban Ocon outpaced team-mate Pascal Wehrlein by nearly a second on his Manor debut as he finished 16th quickest.

It was a disappointing morning for McLaren with Jenson Button 18th and Fernando Alonso failing to set a timed lap.

Alonso's session ended early when Honda discovered a water leak on what was a new, upgraded power unit.

The Japanese manufacturer decided to swap out the whole unit to carry out an investigation into the problem, which it does not believe is a consequence of the update but rather an issue with a single part.

Several teams also tested a prototype tyre for Pirelli during the 90-minute session.

F1's tyre supplier has developed a new construction it says is more resistant to impacts from kerbs and has given teams four sets of the rubber to try across FP1 and FP2.

FIRST PRACTICE RESULTS: