Russian returnee Daniil Kvyat put his Honda-powered Toro Rosso on top of Formula One's testing timesheets at the Circuit de Catalunya on Wednesday with the fastest lap yet in 2019.
After former Ferrari driver Kimi Raikkonen led the way for Alfa Romeo in the morning, Kvyat went quicker at the end of the day with a lap of one minute 17.704 seconds on the softest and fastest type of tyre.
"We always knew we were going to end up P1," joked the Russian, who was dropped by Toro Rosso in 2017 and spent a year as a Ferrari simulator driver before being given another chance by the Red Bull-owned team.
"The priority was not that (to be fastest) but to bounce back after the first day which wasn't ideal," added Kvyat. "Today we covered more (laps) than planned. A productive day."
Kvyat did 137 laps, one less than Raikkonen's top tally but more than Sebastian Vettel's 134 for Ferrari, in an impressive showing for Honda after years of being plagued by poor reliability and performance.
Vettel was fourth fastest, ending his team's run of being fastest every day, but using harder and slower tyres than those above him.
Raikkonen's early 1:17.762 lap marked the first time a team had gone faster in 2019 than they managed in last year's pre-season testing.
Champions Mercedes continued to keep their powder dry, with Finland's Valtteri Bottas the slowest of the nine cars on track before lunch but doing more laps than anyone else -- 88 to Vettel's 80, both on the same medium C3 tyre.
Five-time world champion Lewis Hamilton took over for the afternoon stint using a prototype tyre and did another 94 laps while being faster only than the Williams of fellow Briton George Russell.
McLaren, whose performance has been encouraging over the first two days, missed the first two hours after what they described as "some overnight changes" to the car but managed to get Spaniard Carlos Sainz out for 90 laps.
Red Bull's Max Verstappen did a healthy 109 in his Honda-powered car.
Williams were absent for the morning with their FW42 car only reaching the circuit in the early hours but Russell made it out in the afternoon for 23 laps. His fastest was nearly five seconds slower than Hamilton.