The first day of Formula One testing saw mixed fortunes for Scuderia Toro Rosso.

The day got underway with the team's drivers, Sebastien Buemi and Jaime Alguersuari, unveiling the new STR5 design in the pitlane at the Valencia track.

However, once the car (which is the first to be designed in house by the Italian based squad) took to the track problems soon started to appear.

Swiss Buemi had only completed ten laps of testing before he had to return to the pits with what turned out to be a gearbox control problem.

The problem took much of the day to fix before Buemi and the car reappeared in the final hour of the session, recording a best time of 1m14.762 in the additional eight laps he completed but still over two seconds slower than the session's best mark, put down by Felipe Massa in the new Ferrari.

“This morning we had a problem with one of the gearbox actuators, which we managed to improve, but not fix completely,” explained technical director Giorgio Ascanelli. “It is too early to make any comment on the actual performance characteristics of the new car. In the short term, we will be trying to fix the actuator problem overnight, in the hope of having a better day tomorrow.”

“It's good to start testing at last,” added Buemi. “This morning, we had a problem, which took a long time to analyse. We managed to get out again towards the end of the day, even though the fault was not completely fixed.”

“At least we managed some running, which allowed us to work through the usual new car procedures, such as checking seat position, visibility from the cockpit, the systems and so on. But it is a bit too early to get an impression of what the car is like, especially those elements affected by the rule changes.”

Buemi is scheduled to test the car more tomorrow, before Jaime Alguersuari takes first testing laps ever in an F1 car on Wednesday.