Robert Kubica tops the timesheets on the opening day of the final Formula 1 pre-season test in Barcelona as numerous teams hit trouble.
Kubica, completing his final morning of testing for Alfa Romeo before race drivers Kimi Raikkonen and Antonio Giovinazzi take over for the remainder of the time, ended his running by using a set of the C5 compound tyres, the softest available, to complete a qualifying simulation. His 1:16.942 effort being enough to place him atop of the times.
At Red Bull, Alex Albon saw his running severely limited after a problem on his early installation lap saw him trapped in the pits for three of the four hours. The problem was mirrored at sister team Allpha Tauri where Pierre Gasly had similar problems.
Both teams have said the problem was nothing to do with the Honda power unit but, as both cars emerged back on track within moments of each other, the speculation will linger.
Lewis Hamilton completed the most laps of anybody in the morning. Again, Mercedes focused on race simulations so, despite only being +0.620 off the time of Kubica, little can be read into this position.
The story was similar at Racing Point, Renault and McLaren, but the two red flags seen on Wednesday morning came as a result of problems for Ferrari and Williams.
Vettel, who was sixth fastest, spun off track but was quickly back out on track, the source of the problem not made public, but Latifi for Williams appeared to have a hydraulic problem, possibly similar to that which he suffered during the first test last week.