World Championship leader Lewis Hamilton topped the timesheets on the first day of testing at Monza.
Ten teams were in action on a day when the air temperature hit 31 degrees, and with the humidity making conditions almost unbearable, even for locals.
That said, following predictions of rain showers today, and heavier downpours forecast for tomorrow, there were a few spots of rain mid afternoon, before a heavier shower in the closing half hour of the session.
Following suggestions from the Grand Prix Drivers' Association (GPDA) the second chicane, scene of numerous incidents over the years, including a multi car crash a few years back which resulted in the death of a marshal, has had the gravel removed and the run off area covered in asphalt (above and below). According to sources at the track there no plans for any further modifications until after next week's Grand Prix.
Hamilton was on duty for McLaren as the Woking team started to work through a preparatory programme for next week's Italian Grand Prix.
The test focused on the low downforce configuration that will be used for the race on the legendary high speed circuit, alongside various aerodynamic upgrades. Some tyre evaluation also took place, with the track traditionally tough on durability.
The Englishman's programme during the morning session was temporarily interrupted with a CV joint failure, however he returned to the track soon after.
Kimi Raikkonen was on duty for Ferrari, the Finn concentrating on defining the set-up for the F2007 and on development of aerodynamic solutions aimed specifically at this track.
Raikkonen, who finished second at Istanbul on Sunday, completed 60 laps, finishing just 0.146s off Hamilton's pace.
Third quickest, and looking very strong here, was Nick Heidfeld in the BMW. The German team tested a low downforce aero package consisting of a new front and rear wing as well as modified bodywork.
Heidfeld started the day working out a baseline set-up. In the afternoon he made various aerodynamic comparisons which enabled the engineers to gather specific data. His best time was just 0.165 shy of Hamilton's best.
After a bit of a set-back in Turkey, Toyota was looking altogether stronger today. Jarno Trulli suffered some electronic issues early in the day but then concentrated on establishing a baseline for the low downforce package that is crucial to strong performance here.
Braking performance and feel is key to the driver at Monza as he stops the car for the three chicanes that intersperse a track that is full throttle for much of the lap. Without the levels of aerodynamic downforce normally on the car, the emphasis is on establishing a set-up that inspires confidence. There is a compromise to be reached between running the car low and stiff to optimise efficiency and giving the driver a degree of comfort over Monza's high kerbing. The Italian will continue work adjusting to the low downforce package tomorrow.
"The car has quite a 'light' feel at Monza because you run with the bare minimum of aerodynamic downforce because so much of the track is flat-out," said Trulli. "In general we got through a decent amount of work on the set-up today before the rain came at the end of the day. We worked on the tyres and brakes and I was am happy with progress. The second chicane now has a tarmac surface instead of gravel and it is good to see that - a definite step forward."
"We have a busy programme here, where the car runs in a substantially different configuration from the other circuits on the F1 schedule," added test team manager, Gerd Pfeiffer. "We made a decent start to the test with no significant hold-ups and strong reliability, with just some rain at the end of the day bringing us to a halt around 20 minutes before we planned. We have collected a lot of data which we can analyse this evening before continuing with Jarno in the car again tomorrow before Ralf takes over on Thursday."
Kazuki Nakajima was the busiest driver today, the Williams test driver completing 98 laps .The Grove outfit was one of several teams trying out a wide range of new aero solutions, most significantly a McLaren-style wing over the nose.
We ran through day one's planned test programme with no problems at all," said test team manager Dickie Stanford. "In fact, it's probably been one of the smoothest and efficient sessions we've had so far this year, with Kazuki completing the most number of laps of the session.
"Alex will be driving tomorrow so we will spend this evening setting the car up for him," he added.
Although he has taken part in the last two Grands Prix as Toro Rosso driver, today was actually Vettel's first ever test session with the team.
The Italian team worked on its Monza-specific downforce package in addition to working on brakes and carrying out general set-up work, all on the one type of Bridgestone tyre.
The main item on Red Bull's agenda was aero work, both general and Monza-specific. The original plan had not included a tyre comparison, but the threat of rain meant that Mark Webber did in fact try both types of Bridgestone dry weather tyres today.
The morning was trouble free, but an electrical failure led to some loss of track time in the afternoon.
While the priority for Renault is to prepare for the next two races on European soil, in particular the Italian GP, the French decided to concentrate on the 2008 electronic set-up on its first day of testing. This included running the standard ECU, which will become compulsory next year, and which Ferrari has already tried.
Nelson Piquet went out without any driver aids to provide the team with his initial impressions. He did several runs - generally long ones - and concentrated on setting up the car in this configuration. The data recorded will be analysed by the team this evening, and again when it gets back to the factory in the framework of its 2008 project development programme.
As the clouds began to gather this afternoon the team decided to partially revise its programme and began testing for the Italian race as the weather forecast for the next two days is not very promising.
The team was able to complete its programme without any difficulties. Nelson quickly got back into his stride in this set-up and by the end of the day he had covered 94 laps, almost 542 kms, and set the 7th-fastest time.
"The car was not really different," said the Brazilian, "it was just a bit less predictable and slightly trickier to drive as it is less forgiving! It's difficult to be consistent as the laps unfold but I think I got to grips with it fairly quickly. We've revised the braking load to adapt the car to 2008, and we concentrated on setting it up in this configuration. I think we've done a good day's work today with a lot of laps covered.
"It was really heavy today at Monza," admitted Christian Silk. "Our programme went off with any hitches, and we've recorded interesting data on our first day's testing in 2008 configuration. The car was reliable and the new on-board electronic systems worked without any problems so we managed to cover a lot of laps. In the late afternoon we began our preparation for next week's race as we're afraid that track conditions will deteriorate from tomorrow."
Rubens Barrichello was on duty for Honda, the Brazilian completing 83 laps and finishing 1.36s off the pace, marginally ahead of the Super Aguri of James Rossiter.
Barrichello focused on establishing a good set-up for the RA107, alongside working through aerodynamic and suspension evaluations.
Rossiter spent the morning evaluating the aero package for next weekend's race and completed a programme of set-up work and race starts in the afternoon.