Grosjean completed a seat fit at Mercedes’ factory earlier this month ahead of a farewell test at Paul Ricard in June.

The Frenchman was keen to have one last test outing in an F1 car after his dramatic, fireball crash in the Bahrain Grand Prix last year, which forced him to miss the final two races of 2020 as a result of the injuries he sustained.

Mercedes organised a test for Grosjean to drive Lewis Hamilton’s 2019 title-winning car at the French Grand Prix, but this is now in doubt after F1 has rescheduled its calendar following the postponement of the Turkish GP.

With the French GP set to take place a week earlier, it clashes with the Road America IndyCar weekend - with Grosjean currently competing in the series.

F1 2021 | Formula One latest news | Perez needs more time, Vettel hopeful for success in 2021

Speaking on F1’s Beyond the Grid podcast, Grosjean admitted he was immediately impressed by what he experienced during his short visit to Brackley.

“I got to the factory and I was amazed by the facilities, the way people are working around it. After five minutes within Mercedes in Brackley, I could understand easily why they were the most successful sports team in history, I think.

“Find another team, whatever sport, that has been winning as much as Mercedes has done. It is almost impossible. Therefore, getting in there and seeing and understanding it, it is very clear.

“Even though this year everyone in Bahrain testing was like ‘Red Bull is faster,’ here we go, with three races done – Mercedes two, Red Bull one. That is the strength of that team. They may not have the fastest car but they will always find a solution around that and you feel it when you are there.”

Grosjean enjoyed a long F1 career, starting in 2009 with Renault having replaced Nelson Piquet Jr. mid-season.

He returned in 2012 with Lotus after securing the GP2 Series title in 2011, before moving to Haas at the end of 2016 - where he remained with the American outfit until 2020.

Explaining what the differences are between the teams he drove for and Mercedes, he added: “I would say it is the culture at the top. Then from there, the detail is pushed to the maximum. Everyone is really trying to get the solution, to find the solution to go faster.

“Obviously, the facilities are incredible but I guess many teams can have the facilities but then it is just how you use it, how you optimise it.”