Conditions for the fourth day of testing at Jerez de la Frontera, were ideal, with blue skies, constant sunshine, and temperatures creeping up to 17 degrees C.

It was good news and bad news for Toyota, with Ricardo Zonta topping the timesheets, having posted the third fastest lap of the week, but in the 2004 car. While Jarno Trulli, driving the TF105 for the first time, could only manage seventh fastest, 1.7s off the pace.

That said, Trulli was familiarising himself with the car - spending most of the day working on set-ups - and did outpace both BARs, which were also running in 2005 spec.

Behind Zonta, Kimi Raikkonen and Juan Pablo Montoya entered the first round of what many fans believe could be one of the most fascinating battles of the year, the struggle for supremacy at McLaren.

Although round one went to the Finn, his Colombian teammate was hot on his heels, ending the day just 0.132 behind.

Both drivers were running MP4-19Bs, as they went head-to-head for the first time, and though the media appears to want to build on the rivalry between the two, making full use of the 'fire and ice' concept, both drivers appear to be getting on well outside the cockpit. Team sources say that the two drivers are working very well together and that their feedback is superb.

The other head-to-head was down the pitlane at WilliamsF1, where Nick Heidfeld out-paced Antonio Pizzonia, but only by 0.129s. However, for the second successive day, Pizzonia suffered mechanical problems which limited his track time, the Brazilian completing 94 laps, compared to the German's 146.

"We had a much more productive session today," said test team manager, Tim Newton. "Antonio spent the majority of the day evaluating various new systems on the interim FW26, while Nick returned to the track today and worked on different set-up options on the car. Both drivers also carried out tyre testing for Michelin."

Sixth quickest was Franck Montagny, whose programme consisted of the final phase of the week's tyre testing programme, conducting long-distance evaluation of 2005 tyres on runs of approximately twenty laps.

"We had another productive day of tyre testing," said Christian Silk, the French outfit's chief test engineer, "reaching a race distance with 2005 spec tyres and recording promising results.

"We have made good progress again this week, and the car ran without problems, averaging around 530 km per day."

On its last day of testing before its 2005 car is launched, BAR had Enrique Bernoldi and Jenson Button on duty. Both drivers, at the wheel of the 'concept car' focussed on electronic and tyre work. The English driver carried out a number of long runs, while the Brazilian, who was running a race simulation, encountered a mechanical problem which limited his track-time. That said, he outpaced his teammate by 0.308s.

Propping up the timesheets, 2.3s off the pace, was Ferrari's Marc Gene, who crashed heavily on Wednesday. Today, the Spaniard continued to work on a development programme of electronics, new components and Bridgestone tyres.

Today's Times