Spanish GP F1 practice: Lewis Hamilton leads Mercedes 1-2 in FP3

Hartley brought the on-track action to a premature end after spinning his car into the barriers at the fast Turn 9 right-hander with a couple of minutes remaining.

That locked in Hamilton and Valtteri Bottas at the top of the order, a couple of tenths clear of Ferrari's Sebastian Vettel.

Mercedes held the top two positions for the first half of the session as Hamilton led Bottas by 0.029s on a 1m17.844s after their first runs on soft tyres.

That was enough to head the Ferraris at that stage despite Vettel and Kimi Raikkonen running supersofts, while Daniel Ricciardo went fifth on mediums as the three top teams diverged on tyre compounds.

Vettel and Raikkonen briefly established a Ferrari one-two after bolting on fresh supersofts, but when Mercedes switched to the same rubber its drivers moved back to the top.

Hamilton's 1m17.281s was enough to beat Bottas by 0.15s and lap just over a quarter of a second quicker than Vettel.

Bottas improved on the same set of supersofts to close to just 0.013s behind Hamilton, who went wide at Turn 1 and had time-consuming slides through Turn 13 and exiting the Turn 14/15 chicane before the final corner on other laps.

Ricciardo switched from mediums to supersofts at the very end of the session and wound up fifth, 0.7s off the pace, as Kevin Magnussen claimed sixth for Haas.

Magnussen's team-mate Romain Grosjean had a messy session with a big trip through the gravel at Turn 2, but he overhauled Fernando Alonso's McLaren to take seventh.

Carlos Sainz Jr also cleared Alonso in the dying minutes of the session as Renault looks to recover from a difficult Friday.

Sainz had a near-miss with his team-mate at Turn 13 when Nico Hulkenberg arrived at the corner at full-speed and Sainz was moving slowly.

Pierre Gasly completed the top 10, while Hartley's crash prevented any final improvements.

Hartley touched the grass on the entry to the fast right-hand Turn 9 and spun sideways across the gravel into the barriers on the outside.

He emerged unscathed, although the team has a significant rebuild job to get him out for qualifying after the car sustained extensive damage, with the entire rear axle hanging off as it was recovered.

Max Verstappen was dumped to 12th in the second Red Bull.

His session then ended early after a suspected electrical problem, and he was also placed under investigation (and subsequently cleared) after running wide at Turn 1 and not staying to the left of the bollard that is positioned to stop drivers cutting the corner.

The two Williams drivers propped up the times again, with Lance Stroll suffering another excursion into the gravel.

Stroll ran wide at Turn 4 after a wobble on corner entry, although stopped before the barriers and managed to get his car back to the pits.

FP3 times