George Russell, at the wheel of the Mercedes W10, topped the timesheets on the final day of tyre testing in Abu Dhabi as the 2019 season concludes.
The Briton completed 145 laps, the second-most laps of the day, on his way to posting a best time of 1:37.204, just 0.080s off Valtteri Bottas' best from yesterday, as the German team continued to analyse and understand the tyres for the 2020 season.
"It's been a pleasure driving the championship-winning W10 today," said Russell. "We tested the 2020 tyres and I've learned a huge amount about them which I'm sure will help both myself and the team going into next season, which is very positive.
"It's been an enjoyable day at the track and I'll get more track-time in next week when I'll do the tyre development test for Pirelli before my season finally comes to a close.
"I'm excited for a few days off to relax a little before I'm back to my training regime to get the best possible preparation for 2020.
"My first season in Formula One has been a steep learning curve and I'm already looking forward to Australia when we go racing again next year."
It was good to be able to work with George again today," said Andrew Shovlin, "and he did a great job to get over 800 kilometres and fastest lap of the day.
"The car has run faultlessly over the last two days which has allowed us to get through a lot of work. We spent more time today working on getting the most out of the 2020 tyres and we have made good progress in understanding what they need in terms of set-up.
"We also completed a compound scan in the morning which gives us some data to select the tyres for the opening races and did some work on the softest compound - the C5 - on which George set his fastest lap.
"That's not quite it for the W10 as we will be converting Valtteri's race chassis over the next few days into the mule car to do our first 18-inch tyre development test for Pirelli.
"George is going to stay here to do the driving for that test, so it's been very useful to him to get familiar with our car today in preparation for that work which starts on Sunday."
Charles Leclerc finished the day a couple of hours earlier than planned, after he crashed into the barriers at Turn 14. He emerged unscathed, however there was quite a bit of damage to the SF90.
Once the extent of the work required to get it track worthy again had been assessed with the car back in the garage, it was decided to call a halt to the test.
Up until then, Charles had completed 103 laps, almost double the race distance from Sunday's Grand Prix, giving the team plenty of data.
As was the case yesterday, when Sebastian Vettel was in the cockpit, Leclerc began by driving around 20 laps with various measuring devices fitted to the car. On the stroke of ten, the test became exclusively limited to tyre evaluation and Leclerc started a series of runs, comparing the 2019 tyres and the compounds Pirelli is working on for 2020.
The morning programme ended at noon, at which point various components that had reached the end of their life were replaced, before getting the car back out on track at 13:00. Leclerc continued work on tyre evaluation, with short and long runs to evaluate them in all conditions.
Leclerc and his SF90 covered a total of 103 laps, posting a best of 1:37.401 on the C5 compound, which ended up being the second fastest time of the day behind Russell.
The crash at turn 14 came around 16:00 when the youngster lost control going over a kerb.
"This was our last day on track and I think it was useful, despite the accident which meant I had to stop early," said the Monegasque driver. "We did a lot of comparison testing of the 2020 tyres up against this year's and acquired a lot of data which will now be analysed in depth.
"Now we can switch off for a while, but I will never forget my first season with Ferrari and I'm sure that it won't be long until I want to be back on track."
Third quickest was Lance Stroll in the Racing Point, the Canadian completing 132 laps on his way to posting a best time 0.795s off Russell's best on the same tyre compound.
Having run Daniil Kvyat and Sean Gelael yesterday, today Toro Rosso had Pierre Gasly on on duty. The Frenchman completed 146 laps, the most by any driver today, posting a best time 0.962s down on pace-setter Russell.
"Another good day of testing," said Sunday's star, Carlos Sainz, who completed 112 laps in the McLaren. "I obviously have good memories from the 2018 Abu Dhabi test when I jumped into a McLaren for the first time.
"Also, testing again this year has given me a chance to compare and feel the progress we've made since last season. But apart from that, the test day itself ran smoothly trying the compounds.
"In general, I'm pleased and happy with how everything went. A big, big thank you to the mechanics and the team for the effort that they've put in during testing with all the long hours. It was great to sign off the 2019 season with 112 laps and a lot of data for next season."
"Another productive day," added Andrea Stella, "and although we had little delays, we again clocked up over 600km and ran without any major issues to entirely accomplish our set programme.
"Over the two days, we've learned extensively about the 2020 tyre and have been able to compare them with the current tyre - important information that will be extremely useful to both Pirelli and ourselves.
"A good end to 2019 and a big thank you to everyone here in Abu Dhabi and also back at the McLaren Technology Centre for their tremendous efforts this year."
Back on duty again with his new team, Esteban Ocon completed another 128 laps, bringing his two-day tally to 205 laps as he continued to acclimatise to the car and the team.
While the test primarily focused on evaluating Pirelli's 2020 tyre range and running comparisons with this year's compounds, for the team, it was beneficial to bed Ocon in before the winter break with pre-season testing in Barcelona just 76 days away.
"It's been a busy two days," said the Frenchman, "with a great outcome to write 2019 off with a nice ending. Today, especially, was very productive; it was probably worth two days of testing. We worked through a lot of things, which was very useful.
"I was getting used to everything again and growing more comfortable on each run," he continued. "There were some important details cleared on my side and we also identified some areas we need to work on over the winter.
"I would like to thank Renault for this opportunity, I wish all the team a great winter after a busy season and I look forward to seeing them again soon."
"This week's test has been very good with Esteban in the team," added Sporting Director, Alan Permane, Sporting Director. "We drove 205 laps, and Esteban, running faultlessly.
"You wouldn't know he hadn't been driving regularly, given his excellent fitness and ability to keep consistent. His feedback was good, and we had no issues at all.
"It means we are well prepared for our winter campaign and we can go into next year ready to hit the ground running."
Alex Albon took over the Red Bull from teammate Max Verstappen, the Thai driver completing 139 laps on his way to posting the seventh best time of the day, albeit, like Ocon, on the 2019 C4 tyre.
Check out our Wednesday gallery from the Yas Marina, here.