Ex-sporting director Eric Boullier claims Honda was so "unprepared" for Formula 1 return, he warned McLaren the project would need several years.

The British team rekindled their once dominant partnership in 2015 with then-CEO Ron Dennis believing it would be impossible to win a championship as a customer of Mercedes.

However, after three seasons of poor reliability and performance, the two parties would split and Boullier, who left McLaren last summer, admits the writing was always on the wall.

“Already in the first meeting, I realised how unprepared they were for the enormous challenge they faced,” Boullier told France’s Auto Hebdo.

“I told Ron Dennis immediately that we would need at least three or four years of development to get to the top, but the contracts were already signed and Dennis was sure he could relive past successes.

“The current engines are very sophisticated and only Mercedes was ready to outperform the competition based on years of development.

“The union between McLaren and Honda could not have come at a more complicated time in terms of the technical-historical moment.”

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Now the Woking-based outfit is run by a new CEO Zak Brown, who instigated the Honda divorce and made the current deal with Renault for engines.

However, that had little impact on their competitiveness as the team struggled again in 2018.

“We realised in April [last season] that we had completely missed the mark with the car,” Boullier recalled. “We found serious problems in the correlation of data and no solution until it was too late.

“In some respects, we were less competitive than in 2017, which was difficult to cope with.”

As for Honda, free of McLaren's limitations, they have flourished in a new partnership with Toro Rosso initially last year and scored their first podium since 2008 with Red Bull in their first race together in Australia.