In terms of reliability and consistency we know that Mercedes is still 'up there'.

However, other than a question mark over the car's handling, the team admits to concern at tyre graining, though it is convinced that this is an issue that will affect its rivals also.

Speaking after the opening test, Valtteri Bottas was adamant that if Mercedes is to take on Ferrari head-on it would need a raft of upgrades in order to improve the car's handling.

His wish was their command, and at the start of this week's testing virtually every aero part on the W10 was new, and while Bottas admits that improvements have been made, he is seeking more.

"It's better," he told reporters in Barcelona, "but is it enough... that’s the big question mark.

"Definitely you can feel improvements since last week with the stability of the car, with the overall downforce of the car," he continued, "but we definitely feel we still haven’t unlocked everything there is to unlock.

"From last week to this week, definitely we have been able to improve the overall balance of the car," he admitted, "and the differences in the balance we had through the speed range. We've been able to improve overall grip, downforce, and stability. But in all those areas, we can still do better.

"It's not the perfect car yet, but we feel the potential is there. Maybe it's another car that has quite a small sweet spot, but once you hit it, it can be very quick.

"We are learning massively every day, I feel like it's been a good step, every time I get back in the car it gets better. I hope I can feel that again this afternoon and tomorrow and hopefully for a bigger step in Melbourne."

"They still seem strong," he said of Ferrari. "It’s as always from testing to Melbourne a lot of things can change, but they do have a strong package.

"We need to unlock more from the new package to be able to really compete with them properly," he insisted. "At this point I think they’re looking very strong, but there’s still a couple of weeks until Melbourne.

"Red Bull seems in good shape as well," he added. "I think between us two, the differences are not massive, from testing it's difficult to read in detail, but my feeling, our feeling, is Ferrari is a bit ahead of both of us.

"The whole field looks like it's a bit tighter than, for example, last year or the year before," he said. "It's only guessing, you never know what people bring to Melbourne."

Check out our Thursday gallery from Barcelona, here.