Mercedes has conducted a full day of ‘proper’ testing in private at Barcelona with the new W03 today.

Between them Nico Rosberg and Michael Schumacher logged over 300kms of running.

It follows a filming or shakedown day at Silverstone last Thursday. But while that was conducted on Pirelli’s demo tyres, today’s test was a pukka test day on race rubber, and there were no mileage restrictions.

In effect the team has gone some way to catching up with rival teams who finished their cars on a normal schedule, and ran at Jerez earlier this month.

Mercedes planned some time ago to use the old car in Jerez, giving itself almost two weeks of extra R&D time before key elements of the W03 were finalised. It also allowed the team to make extra use of ex-Ferrari designer Aldo Costa, who only joined on December 1.

It’s also been suggested that the team wanted to keep a few secrets under wraps for as long as possible.

Although the reduced running with the new car is obviously a handicap – with only the two four day tests at Barcelona still to come – Mercedes won back an extra day with the W03 by using only three of the four available days at Jerez with the old car.

Under the testing agreement, missing that day earned the team a private test, which it utilised today – with no prying eyes and no red flags caused by others to disrupt running.

The team now has all of Monday to work on the car and crunch the data collected today before running again on Tuesday with the rest of the teams – which means it should be in pretty good shape when it joins its rivals…