Raikkonen has seat fitting at Sauber

The 2007 world champion is based close to Sauber's Hinwil base, so it made sense for Raikkonen to make an early visit to the facility before an intense end-of-season flyaway schedule.

Sauber and Ferrari's close technical collaboration also meant there was little concern about potential team secrets passing to the customer outfit.

Sources have revealed that Raikkonen visited the factory on Friday for meetings with senior staff, and create a seat-fitting mould that can then be used around him in the cockpit of the 2019 design.

Having a seat ready also opens up the possibility of Raikkonen testing Sauber's 2018 car later this year at a tyre test.

Last week, Raikkonen sat out Pirelli's Paul Ricard test with Ferrari - which instead ran 2019 signing and current Sauber driver Charles Leclerc before he handed over to Sebastian Vettel.

It is possible, therefore, that Raikkonen could receive the return favour during a Pirelli tyre test that Sauber will be complete in Mexico after next month's race.