Lewis Hamilton edged out Kimi Raikkonen and Michael Schumacher on day one of the final pre-season Formula One test.
The three-day session in Barcelona is the last chance for teams to fine-tune their cars ahead of the curtain-raising Australian Grand Prix on March 16.
McLaren star Hamilton clocked one minute 22.276 seconds, with world champion Raikkonen 0.043secs behind.
Schumacher, testing Ferrari's new car in his advisory role, was third quickest with a time of 1:22.428.
Williams' strong pre-season continued as drivers Kazuki Nakajima and Nico Rosberg were fourth and sixth, sandwiching the second McLaren of Heikki Kovalainen.
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All three drivers dipped under 83 seconds at the 4.655km Circuit de Catalunya.
Double world champion Fernando Alonso in his Renault and the BMW Sauber of Nick Heidfeld had the seventh and eighth best times, with Force India's Adrian Sutil ninth.
It was the on-track debut for the VJM01, named after co-owners in Indian billionaire Vijay Mallya and Dutch entrepreneurs Jan and Michiel Mol.
"We were running 60% of the aero package we will use in Australia [for the first race] and it seemed to go well," said technical director Mike Gascoyne in a statement.
David Coulthard brought up the rear of the 19 drivers in his Red Bull, although technical problems resulted in him completing only 25 laps.
Security was stepped up to a new high for testing at the Circuit de Catalunya as organisers sought to avoid a repeat of the racial abuse suffered by Hamilton earlier in February.
The British driver received a wave of racial taunts from a group of Fernando Alonso fans at testing three weeks ago in Barcelona and world governing body the FIA responded by announcing their 'Racing Against Racism' campaign.
Monday's test session passed without incident and a smiling Hamilton briefly appeared after lunch to sign autographs for several Spanish fans who had waited to greet him.
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