Renault Sport boss Jerome Stoll says the French manufacturer underestimated the massive task that followed its buy-out of Lotus and return to F1 as a works outfit in 2016.

Upon its decision to return to the Grand Prix battlefield, Renault developed a five-year plan destined to propel the team to the front of the grid.

While the yellow squad continued its progress in 2018, concluding its campaign as 'best of the rest', it still remains at a fair distance from F1's unassailable trio of front-runners, Mercedes, Ferrari and Red Bull.

Stoll, who will retire at the end of the year as president of Renault Sport, underlined the team's achievements, but also the challenges that it faced just months after acquiring the failing Lotus outfit.

"We largely underestimated the state in which the team was in," he told Auto Hebdo.

"Many people had left, very little investment had been made. We knew it was going to be difficult, but we ended up in a much more difficult situation than expected."

As part of its long-term ambitious plan, and under the guidance of the tireless Cyril Abiteboul, Renault embarked on an extensive restructuring of its Enstone and Viry-Châtillon units.

"Thanks to Cyril Abiteboul, who has been able to give the impetus, we are a team with a very special identity and it is something that makes me proud," said Stoll.

"We were ninth in 2016, sixth last year and fourth this year, which is a first step in which we have set up all the foundations.

"The next step for Renault is the podium."

Gallery: The beautiful wives and girlfriends of F1 drivers