Tough 2015 F1 season brought McLaren and Honda closer together

Boullier has confirmed McLaren and Honda realised as soon as the first pre-season test in Jerez that a troubled year was in store.

"At that stage we had a lot of meetings, we assessed the entire programme, and we reinforced straight away from Jerez, and in particular from the [final] test in Barcelona, the co-operation between McLaren and Honda," Boullier told Autosport.

"It was drafted in the contract, but we made clear straight away we would stick together much more, and come the end of testing we had a second push for this co-operation.

"We then understood the plan for the season would be to work together, and that is basically what happened.

"Thanks to that move it reinforced the co-operation between the two companies, and at a technical and engineering level, there was then very good communication and a good merge."

Honda motorsport boss Yasuhisa Arai claims Honda's struggles were impacted by the fact it entered the sport after a seven-year hiatus.

It also did so at a particularly challenging time when a new engine formula had just been introduced.

"We did not have enough experience about the current Formula 1," Arai told Autosport.

"We have lots of experience from other eras, but after 2008, we left and the technology dramatically changed.

"We could not catch up. That is a big gap. No experience during that seven years put us behind."