Bernie Ecclestone, Formula One's chairman emeritus, said: 'The Renault deal is all done. Alonso staying is super news.
'But I can't see why McLaren will be any happier with Renault than they are with Honda. It wasn't Honda's fault things didn't work out, it was McLaren's. Every day they had a fight about everything, instead of working with them, which was a little bit stupid.'
Nonetheless, McLaren will trumpet the news loudly, believing the developments are the most important of the team's post-Ron Dennis era.
Executive director Zak Brown has played a key part in the Alonso-Renault negotiations under the direction of the team's executive board.
In other parts of the jigsaw, Spaniard Carlos Sainz, 23, is set to leave Toro Rosso to join the Renault works team for the next-but-one race in Malaysia, casting doubt over the future of Britain's Jolyon Palmer. Honda will then power Toro Rosso next season.