Bahrain F1 test: Daniel Ricciardo leads morning for Red Bull

The Australian's programme just before the lunchbreak was a series of short runs and it was on one of these that he set the best time of 1m32.349s with super-softs to knock Lewis Hamilton's Mercedes off the top of the timesheets.

Hamilton had bounced back from an early morning problem that brought out a red flag to get on with his intense programme.

With Mercedes determined to use this week's running to get a better understanding of tyre management, its day did not get off to the best start when Hamilton's W08 came to a halt with an 'electrical disconnection' just 15 minutes into running.

There was further frustration when it took track officials nearly 25 minutes to get his car back to the pits.

But with the issue quickly resolved, Hamilton was able to resume running.

In the end, his best lap of 1m32.822s was 0.473 seconds slower than Ricciardo.

Nico Hulkenberg spent the morning conducting aerodynamic testing for Renault and ended up third fastest, with the team eager to find improvements to its car to help with its long-run pace.

Fourth fastest was Williams's Lance Stroll, whose main focus was on tyre management as he spent the morning experimenting with ways to better understand and manage the Pirellis.

Romain Grosjean returned to action for Haas and was trying new products from brake supplier Carbone Industrie, as the American team weighs up whether or not to switch from Brembo.

Testing runs until 6.10pm local time on Tuesday thanks to a 10-minute delay to the test getting under way in the morning after shipping containers had been left in a dangerous position at the end of the pitlane.

The only other red flag of the first morning was caused by Toro Rosso test driver Sean Gelael, whose car suffered a suspected engine failure after four laps.

A fresh Renault power unit was fitted for the Indonesian to return to action later on.

There were also engine woes for Honda too, with McLaren development driver Oliver Turvey only able to complete two installation laps in the morning.

Honda had discovered a water leak in the ERS, which has prompted the need for a replacement power unit to be fitted.

TUESDAY MORNING TIMES: