Key to the preliminary contract agreement signed in Monaco; a clause enabling Red Bull to pull out should the Honda upgrades for Canada not perform as expected. Both parties have obvious reasons as to why this hugely important agreement hasn't been made public as yet.

Firstly Red Bull are still contracted to use Renault power units, but also Honda would not like to be seen to fail a top team yet again should the Canadian Grand Prix upgrade not deliver the required performance and reliability. It is clear that working with a low profile team such as Toro Rosso takes the heat off Honda (unlike working with McLaren!), so this type of methodical planning and deal making can occur unhindered.

Renault are unaware of this, officially, but of course suspect that Honda are in with the serious shout with Red Bull from the rhetoric we've heard in the media, particularly during the build up to the Canadian Grand Prix. Veiled threats on whether the new upgraded Renault power unit would be supplied to their former number 1 team for the race in Montreal. But also the hurry up issued by Renault boss Cyril Abiteboul on Red Bull’s final decision on engine supply. A hurry up that prompted a sharp and telling response from Helmut Marko.