McLaren racing director Eric Boullier has labeled the team's partnership with Honda a "proper disaster" which impacted the company's goodwill and image.
Honda's return to the pinnacle of motorsport in 2015 with the team with which it had enjoyed such a successful spell back in the 1980s held many promises.
But the Japanese manufacturer never succeeded in fulfilling McLaren's expectations in its vain attempts to master Formula 1's hybrid V6 era.
While the partnership's first two seasons were perceived as a work in progress, Honda's inability to deliver the goods following fundamental changes to its power unit last winter inexorably led to McLaren's decision to throw in the towel.
"When you look at the last three years it's been a proper disaster for us in terms of credibility and getting new sponsors," Boullier said in no uncertain terms.
"And then you have to take the long-term view: in the next five years I am absolutely sure that we will go back to where McLaren belongs.
"And with this bouncing back we get our credibility back and it will rebuild our sponsor portfolio. It might take two to three years.
"We are ninth in the championship – with a top engine I think we would be fourth right now and just on the FOM money we could cover the engine side, so it will not be a big risk on the monetary side.
"Thanks to the shareholders who have been brave enough to take a sporting choice and not hurt McLaren. They could have said, 'Let's wait until Honda wakes up'.
Interestingly, McLaren's doubts over its partner's ability to provide a performing and reliable power unit crept in as early as pre-season testing in Barcelona.
"The crucial moment was after the Barcelona testing, when we tried to work and help Honda to improve the situation in a very short time, including having discussions with the other engine manufacturers, and without going into details, it became obvious that they again would miss the target that we had agreed for the season.
"Then by the summer we knew that we had to take a decision, to stay or not to stay. I can't say a date, but there had been a couple of targets missed by summer."
Despite the conviction surrounding its decision to cut its losses with Honda, Boullier insists it wasn't an easy decision.
"The whole story for them, as it was for us, was to recreate the legacy of the past. On paper everything looked right. Just the way it's been done was not right, obviously," he added.
"I am so glad that they have decided to stay in Formula 1 and commit to another team. Personally I feel a bit sad that it didn't work, but these have been very intense three years."
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