Prost: We talked to Sebastian and Valtteri

And also revealed how the French team had contact with Valtteri Bottas and Sebastian Vettel before, the Spaniard inked a deal with the team.

He returns there for a third spell, having won two titles with Renaut, in 2005 and 2006, and a place he calls home. He will 'reside' there until at least the end of 2023.

Prost expects Alonso, who turns 39 later this month, to be still as fiercely competitive and motivated, "Fernando was one of the three top drivers we were talking to - Sebastian (Vettel) and Valtteri also. But Valtteri is driving a Mercedes, it´s difficult for him to leave the Mercedes team at the moment."

"We did not know exactly what was the motivation of Sebastian... but Fernando has always shown his motivation to come back to the team. Even last year, in Abu Dhabi we had a long discussion with him."

Alonso will replace Australian Daniel Ricciardo, who is moving to McLaren next year. Four times champion Vettel faces an uncertain future, with Ferrari announcing his departure at the end of this year.

Prost said he could see Alonso was fired up for a new challenge after difficult years with McLaren following disappointment in five years at Ferrari.

"What happened with Fernando and different teams was my biggest problem and question mark. I talked to Fernando many times about that," he said.

"I really trust him that he´s going to have another philosophy. Two years outside Formula 1, in my opinion, was maybe not bad for him to have a different feeling, different view.

"He knows what he´s going to get in terms of performance of the car, he knows that 2021 is also going to be a little bit difficult. He´s prepared for that... I really think he´s going to be very different than people understand."