McLaren's race against time
In Barcelona, Spain
With the caveat that judging pace in testing is notoriously tricky, a study of the lap times in Barcelona this week suggests that Ferrari have a slight edge on Renault, who have a small advantage over an unsplittable group comprising BMW Sauber, the new Brawn, Red Bull and Toyota.
McLaren? Their car appears for the moment to be a barely credible 0.5 seconds a lap slower than that group - and 0.8secs behind Ferrari.
The test - at Barcelona's Circuit de Catalunya - is McLaren's penultimate test of the winter, and at this stage they should probably be perfecting their set-ups for the first race in Australia at the end of the month and trying out some new developments for the succeeding races in Malaysia, China and beyond.
Instead, the Mole has been told, McLaren are trying to work out why the data from the wind tunnel in which their car's aerodynamics were honed does not match the results from the car on the track.
The Mole's sources say that, essentially, the rear of the car - the diffuser and the rear wing - is not doing what the figures in the wind tunnel suggested it would.
The first sign that something was wrong came when the cars of world champion Hamilton and his team-mate Heikki Kovalainen were fitted with McLaren's 2008 rear wing during tests in Portugal and Jerez in January and February.
These wings are very different from the narrower, taller designs required by the new 2009 rules - which led onlookers from rival teams to wonder what possible benefit could come from running a rear wing for which the car was not designed.
The second sign was Hamilton leaving the pits in Jerez with fluorescent green paint on the leading edges of the car. The reason? So the team's aerodynamicists could get a better idea how the air was actually being blown around the car when at speed.
Now, in Barcelona, McLaren have been running a Mark II version of their diffuser along with a 2009 rear wing.
It is too soon to conclude whether their problems have been solved - and, to be fair, too soon to tell whether McLaren really are struggling as much as they appear to be.
If they are, be in no doubt that if anyone can get out of this, McLaren can. Their clever people and vast resources will fix this lack of rear grip, sooner or later.
But time is fast running out.
The teams have to pack the freight for Australia on Thursday 19 March, before it flies out from Stansted airport on Friday 20. The last team members fly out on Wednesday 25 March, only four days before the race.