The Woking outfit spent three unhappy years married to the Honda power-unit, in a spell which failed to bring a podium finish.
However, their current relationship with Renault has only yielded a P5 finish at best for the papaya machines.
Despite this, Sheikh Mohammed – a representative of McLaren’s controlling shareholder – said that the split is still the right decision.
“It was in the long-term interests of the company,” Mohammed said, despite admitting it was “an expensive decision” at the time.
“We are committed to this. The way we were heading, the change was bound to come.”
The Sheikh admitted that he still had respect for their former engine suppliers, but that the relationship was not working.
“Tremendous respect for Honda but the relationship wasn’t working and so we had a civilised discussion and we decided to part ways,” he added.
“We will see this through. [It is] frustrating, because we are racers at heart, but you just have to power through.”
Despite the issues of the 2018 car, Mohammed believes the team have worked out why they struggled throughout the season.
“We’re confident we know why we haven’t been able to develop this year’s car,” he admitted.
“There is a fundamental problem, [but] we think we’ve addressed it.
“Had we discovered that in April we would have had a B car but it was too late.
“I don’t know if we want to disclose what we have discovered and why.
“But we have taken steps, and the development of next year’s car has helped us understand what went wrong here.”