Formula 1 rookie Alexander Albon posted the fastest time of pre-season testing so far on the final morning in Barcelona.

The British-Thai racer picked up where Toro Rosso teammate Daniil Kvyat left on Wednesday with a 1m17.637s on the C5 tyres, the softest compound in Pirelli's range.

He led Daniel Ricciardo in the Renault by 0.15s, with the Australian the only other driver to use the red-marked rubber.

Mercedes finally offered a glimpse at their potential as Lewis Hamilton used the C4 tyres to finish third but struggled to post consistently faster times as others have done, perhaps hinting at a higher fuel load.

On one occasion, however, a flying lap was spoiled by a near-miss with Robert Kubica's Williams in the final sector, as the world champion took avoiding action by taking to the old circuit.

The most impressive time though still belonged to Ferrari as Charles Leclerc posted the team's best time week, a 1m18.0s, using the C3 compound.

The Monegasque also focused mostly on longer runs using the middle tyre in Pirelli's range, showing strong pace in the 1m19's before dropping off as the stint progressed.

A small off at Turn 5 almost put a spanner in the works but, in the end, Leclerc went on to total the most laps of anyone with 75 to his name over the first four hours.

Antonio Giovinazzi and Romain Grosjean found themselves in a small no-mans land in fifth and sixth, both posting 1m19.5's.

For the Haas driver, the morning was particularly productive with 64 laps after the three stoppages on track on Wednesday due to electrical issues.

Red Bull had a steady start to the final day as Pierre Gasly focused on longer runs in the RB15, just passing the 50-lap mark.

As the Frenchman went out for the first time, Lando Norris would cause a red flag with a slow-speed slide into the gravel at Turn 5 after 20 minutes.

The Briton would get back out, eventually claiming eighth in the McLaren, just ahead of Lance Stroll as Racing Point's rather unspectacular week also continues.

Finally, Kubica focused on slow aero runs initially, which caused the scary moment with Hamilton, but slowly the Pole picked up speed, finishing 1.5 seconds off the rest in P10 with a 1m21.5s.

A full look at the morning standings in Barcelona can be seen below: