Lewis Hamilton has topped a practice session dominated by a lengthy red flag period at the Formula 1 Dutch Grand Prix.

An engine failure for Sebastian Vettel after 16 minutes saw much of the session wasted as the car was recovered.

Concerns surrounding whether the car was electrically safe saw marshals unwilling to touch, elongated the process it took for the car to be recovered.

No sooner had the session begun that Yuki Tsunoda found himself pointing the wrong way, looping his AlphaTauri out of Turn 10.

The Japanese driver lost the back end on cold tyres, his car adorned with aerodynamic measuring instruments on his maiden run.

Esteban Ocon also had an off, his at Turn 11, as the Alpine driver found one of the scarce tarmac runoff areas.

A moment for Pierre Gasly gave a fright at Hugenholz as the AlphaTauri stepped out as he turned into the 19-degree banking.

It skittled him wide, though the race winner was able to gather the car before he reached the barriers which line the outside.

Verstappen was the early pace-setter, banking a 1:12.850s in the Red Bull on the hard compound Pirelli tyres.

Vettel’s session came to an early end when he suffered an apparent engine failure in his Aston Martin, trailing fluid as he rolled to a hold at pit exit.

The incident was covered under double-waved yellow flags for a long period before the red flag was shown – a message that was bizarrely not relayed on the official timing screens.

Earlier, the German had experienced a reported MGU-K problem which the team thought it had resolved.

The session clock continued to countdown as a dejected and frustrated Vettel continued to spray fire extinguishers into the engine bay, marshals putting down quick dry around the apex of Tarzan.

It was a lengthy delay to clear the car as it remained in an electrically unsafe state.

That saw Aston Martin mechanics head out on track to check the car before it was cleared onto a flatbed truck.

Just six minutes remained when the green flag was shown once more, the field forming a traffic jam in pit lane.

Most backed off in the pit exit to build a gap to the car ahead and gain some free air once on track.

The only driver not to head out was Tsunoda, all other 18 survivors on the soft compound tyres.

Predictably, traffic proved a significant issue, though most improved their lap times regardless.

That saw Lewis Hamilton go fastest with a 1:11.500s from Verstappen on 1:11.597s.

Next were the two Ferraris, headed by Carlos Sainz who was just 0.004s slower than the lead Red Bull.

Lando Norris, who’d been fastest when the red flag was shown, was just 11th at the chequered flag – the Brit having an off at the penultimate corner in the final minutes but able to carry on.

He then had another moment when Ocon appeared not to see the McLaren approaching, pushing him off the road.

Daniel Ricciardo was 14th fastest, his best a 1:13.081s while Kimi Raikkonen was the busiest in the session with 20 laps to his name during the truncated session.

The second practice session follows at 23:00 AEST tonight.

Results: Formula 1 Dutch Grand Prix, Free Practice 1