WATCH: First look at new 2017 cars at pre-season testing

Watch as the new Mercedes takes to the track in Barcelona on day one of the first test. Watch as the new Mercedes takes to the track in Barcelona on day one of the first test.

After 81 long days without Formula 1 we had 10 faster, meaner, cars back on track in Barcelona - and you can watch them in action here.

Mercedes racked up by far the most laps of the day with Valtteri Bottas completing 79 on his pre-season testing debut in a W08. Lewis Hamilton then added 73 to take the combined total to 152 - with the Brit topping the timesheets for the day in the process.

Watch as the new Ferrari takes to the track in Barcelona on day one of the first test. Watch as the new Ferrari takes to the track in Barcelona on day one of the first test.

Ferrari held the fastest lap for much of the day through Sebastian Vettel, as the German impressed in what looks to be a reliable SF70-H, also passing 100 laps.

Watch as the new Red Bull takes to the track in Barcelona on day one of the first test, but has to make a hasty return under covers. Watch as the new Red Bull takes to the track in Barcelona on day one of the first test, but has to make a hasty return under covers.

There were problems for Red Bull in the first session thanks to a sensor issue, with Daniel Ricciardo only completing four laps before lunch as the RB13 was wheeled back to the garage. They were back on track in the afternoon despite a battery issue and he eventually finished fifth after 50 laps.

Watch as the new McLaren has to head back to the pit lane with an oil problem in Barcelona on day one of the first test. Watch as the new McLaren has to head back to the pit lane with an oil problem in Barcelona on day one of the first test.

McLaren had a disappointing day - not for the first time in pre-season testing - as a problems with their Honda engine severely disrupted their running. Fernando Alonso didn't set a timed lap until 3.42pm, and finished 10th.

Watch as the new Williams takes to the track in Barcelona on day one of the first test. Watch as the new Williams takes to the track in Barcelona on day one of the first test.

Armed with a Mercedes engine at a high-speed track, Williams impressed. Felipe Massa even held the fastest lap in the afternoon at one stage and was only three tenths off Hamilton's fastest time.

Watch as the new Force India takes to the track in Barcelona on day one of the first test. Watch as the new Force India takes to the track in Barcelona on day one of the first test.

Force India weren't quite as quick but were similarly competitive, with Sergio Perez behind the wheel of the VJM10 on Monday.

Watch as the new Toro Rosso takes to the track in Barcelona on day one of the first test. Watch as the new Toro Rosso takes to the track in Barcelona on day one of the first test.

They were much faster than Toro Rosso, who struggled to match their rivals' speed despite completing more laps.

Watch as the new Renault ari takes to the track in Barcelona on day one of the first test. Watch as the new Renault ari takes to the track in Barcelona on day one of the first test.

Nico Hulkenberg drove his Renault in an official session for the first time, but ninth place wasn't much to shout home about on his debut.

Watch as the new Sauber takes to the track in Barcelona on day one of the first test. Watch as the new Sauber takes to the track in Barcelona on day one of the first test.

As for Sauber, Marcus Ericsson wasn't able to lift the new C36 into midfield as the Swiss team were the backrunners on Day One.

The Sky Sports F1 Digital team will be providing live commentary from dawn until dusk on all days of F1 pre-season testing while Sky Sports News HQ will also deliver live updates from trackside.