Earlier this year, the FIA announced that it had reached a private agreement with Ferrari in the wake of suspicions it had found a way around the fuel-flow restrictions with its power unit.

That secret settlement angered Ferrari's rivals, who felt that a potential breach of the regulations had been swept under the carpet.

The FIA argued, however, that it had decided not to take the matter to a disciplinary hearing because it could not be sure Ferrari had broken the rules and it wanted to avoid a damaging court case.

Speaking at length for the first time about the matter in an exclusive interview with Motorsport.com, FIA president Todt revealed that he pushed F1's technical inspectors hard to try to understand what was going on.

"There was a suggestion by some competitors that Ferrari could be out of the rules," explained Todt.

"So for months our technicians have been on the back of Ferrari to try to understand [if] what they were doing was regular: legal or not legal.

"I must say myself, I put quite a lot of pressure on our [FIA] teams to make as many controls [tests] as needed.

"Saying that, we didn't need to do that, just because somebody who was a kind of whistleblower is telling us. But we need to make sure that each single team is running their show legal."

Todt said that checks on Ferrari ran throughout last season, and included last year's Abu Dhabi Grand Prix where Ferrari was fined for having given an inaccurate fuel declaration before the race.

"We wanted to go to the top of the problem," added Todt. "So we ran very, very complex verifications to try to understand the problem.

"Again we made a control [check] on Leclerc's car in Abu Dhabi and the stewards decided that it was a human mistake, and they imposed the fine. We could say 'OK, that's fine' – but we still pushed a lot to have a full understanding of this situation."

Todt said that while the FIA's suspicions remained until the end of the season, there was little it could do to take the matter further because Ferrari was adamant that it was within the regulations.

Furthermore, the governing body had no evidence to prove that the rules had been broken.

He added: "Most of the top teams were saying 'we want to understand', but they said the most important things is that whatever is understood, the situation will [must] be clear for 2020. So we changed the regulations for 2020 where we were sure that there will not be any kind of ambiguity with the regulations.

"Then when we arrived to the conclusion that we think that what Ferrari did was not legal, which they debated. They said 'it is legal'.

"So I could have decided to give that to the court of appeal [ and the International Tribunal]. We don't know what would have been decided by the court of appeal, it may have taken years, which was not in the interest of Formula 1."

The fear about a damaging court case prompted Todt to decide a private settlement was the preferred route, with Ferrari being given an unspecified sanction.

While Todt has made clear he would be happy for the full details of the case and sanction to be released, he is bound to stay silent without Ferrari's approval.

It is understood that Ferrari has no interest in disclosing technical details about its engine which could prove beneficial to tipping off rival teams about its design secrets.

Article 4.6 of the FIA's Judicial and Disciplinary Rules states: "The prosecuting body and all persons taking part in the inquiry are bound by an obligation of confidentiality vis-à-vis persons or organisations not concerned with the inquiry.

"Nevertheless, the prosecuting body may at any time make public its decision to conduct a disciplinary inquiry and the outcome thereof."

Making a protest

One aspect of the rival teams' complaints that has annoyed Todt is the suggestion that he tried to persuade them not to lodge an official protest.

He is clear that his preferred option was always for a team to bring matters to a head by making an official complaint on a grand prix weekend.

"This is one of the most frustrating things for me, in the [teams] letter, that I said I tried to dissuade them to protest," he said. "We tried the opposite.

"And individually, when I spoke with them, [they admitted] that it is true. I said 'why did you say this is true, why did you write that?'

"So I think it is clear that I encouraged them, if they were not happy, to make a protest. So we could have been relaxed. But nobody did protest."