As Alonso is contracted to Renault to the end of the month, he was not officially due to commence his duties with McLaren until the start of next year.

But given his special bond with the French marque after winning successive drivers’ and constructors’ titles with the team in the last two years, Briatore agreed to the request.

“I have a strong relationship with Renault, and I would like to thank Flavio and Renault who agreed to my request to test one day with McLaren,” said Alonso.

“I’m pleased I was able to drive for them earlier than expected, and I’m now really excited about the future.”

Briatore declared: “Fernando asked me to test one day with his new team to acclimatise himself to the car.

“We enjoy a very good relationship, and considering his work and his fabulous achievements these past two years, we decided to give him this opportunity.”

Sporting white overalls and driving an unbranded McLaren, Alonso completed 95 laps and clocked the third fastest time of the day with one minute 19.747 seconds.

That was just a quarter of a second behind 21-year-old Briton Hamilton who again proved he is adapting to the car very quickly.

Marco Andretti was another debutant after being given a drive by Honda following his exploits in the IndyCar Series this year.

The 19-year-old, grandson of racing legend Mario, claimed second in the Indianapolis 500, won the Indy Grand Prix of Sonoma and finished seventh in the overall drivers’ standings for Andretti Green Racing to earn himself the ’Rookie of the Year’ title.

Andretti drove 67 trouble-free laps to finish 14th quickest, two seconds behind official Honda tester Christian Klien.