Fernando Alonso drove a Formula 1 car for the first time in nearly a year and a half on Tuesday in Barcelona.
The double F1 champion was at the wheel of a Renault, the team he won his two titles with and who he will drive for next season.
He drove the Renault being used this season by the man he replaces, Australian Daniel Ricciardo, who ended the team's nine-year podium drought on Sunday when he was third in the Eifel Grand Prix, and Frenchman Esteban Ocon.
The Spaniard, who won his titles in 2005 and 2006 with Renault, was limited to 100km under the testing rules in a session officially being used to make a promotional film.
"It was really very special for me to get back into an F1 car", he said in a Instagram live broadcast.
"It was a good opportunity for me to feel the car," he said. "Getting back to the speed of an F1 car is not easy, but I felt that I was improving lap after lap."
Alonso's return to an F1 racing car came on the 20th anniversary of his first laps in the class, on the same Barcelona circuit, at the wheel of a Benetton, the team based in Enstone in England which became Renault in 2000.
He scored two of his 32 F1 victories in the Spanish Grand Prix, in 2006 and 2013, and had five further podium finishes on the track.
"It made it special to be back in Barcelona," he said in a team press release.
"I remember the year 2000, I drove the Benetton here with the Enstone guys. Now, in 2020, it's with Renault, so it's a special track and I have lots of good memories here. It's a track I know very well, so it's been a good day."
Alonso had not been in an F1 car since a test session for McLaren in Bahrain in April 2019 and had not raced one since the 2018 Abu Dhabi Grand Prix, also with McLaren, at the end of his 17th season.
"It felt amazing to be able to drive these cars after two years and feel the speed again, how everything comes so fast, corner after corner, the performance under braking and all the things a Formula 1 car has to offer. To feel it once again felt nice."
He agreed in July to rejoin Renault next season when the team will compete as Alpine, the French manufacturer's sports car brand.
"I'm comfortable here with Renault," he said. "Everything is a bit easier when you know the faces and the team".
Since leaving F1, Alonso has won the Le Mans 24 Hours twice as well as the endurance world championship title, all with Toyota. This year he competed in the Dakar rally, finishing 13th, and drove for a second time in the Indianapolis 500 finishing 21st. He retired in his first Indy appearance in 2017.