Jenson Button shattered the lap record in Barcelona during testing, upstaging Michael Schumacher's track return.
Button set the pace in Spain
He became the first driver to break the one minute 15 second-barrier at the Circuit de Catalunya as he powered round in a hybrid BAR car in 1:14.607.
Button was a second quicker than six-time world champion Schumacher - back behind the wheel for Ferrari after a 102-day absence.
He was also two seconds faster than BAR team-mate Takuma Sato.
Test times can be misleading, and only BAR know what fuel loads and tyres Button was running when he set his searing lap time.
But it is a promising outing for the 24-year-old , watched by team chief David Richards, after his initial test this year in Jerez was hampered by engine problems.
Button will help launch BAR's 2004 car in Barcelona on 1 February.
Schumacher was delighted with his first outing since he clinched his record sixth drivers' crown in the season finale in Japan last October.
The 35-year-old German always takes a long winter break to recharge his batteries but has returned insisting his motivation to carry on racing is as strong as ever.
He said: "I was a bit nervous but I have to say it really went well and to see all the guys again was great.
"We are fully on schedule with the work we have planned."
Schumacher was driving an F2003 car and will help unveil Ferrari's latest challenger at their Maranello headquarters in Italy on 26 January.
McLaren's David Coulthard was also in fine form in testing on another Spanish track in Cheste. His time of 1:09.697 was a track record.
F1 testing, Barcelona: 22 January
Jenson Button (GB) BAR 1min 14.607sec (85 laps)
Michael Schumacher (Ger) Ferrari 1:15.410 (95)
Fernando Alonso (Spa) Renault 1:15.506
Ralf Schumacher (Ger) Williams 1:15.736 (63)
Luca Badoer (Ita) Ferrari 1:15.767 (86)
Marc Gene (Spa) Williams 1:15.820 (46)
Juan Pablo Montoya (Col) Williams 1:16.251 (97)
Olivier Panis (Fra) Toyota 1:16.507 (98)
Giancarlo Fisichella (Ita) Sauber 1:16.529 (66)
Takuma Sato (Jap) BAR 1:16.560 (90)
Mark Webber (Aus) Jaguar 1:17.173 (144)