Ferrari will struggle to keep hold of four-time world champion Sebastian Vettel following the departure of technical director James Allison, according to the BBC's Tom Clarkson.

Allison left Ferrari this week in what the team say was a "joint decision".

Clarkson believes this key departure means the Italian outfit will “really struggle” to keep hold of the German beyond his current contract, which expires at the end of 2017.

He said: "He is probably looking at somewhere like McLaren for 2018. Instead of re-signing until 2020 - which was being mooted until quite recently - I can see him looking over his shoulder at what else is out there."

This clip is taken from 5 live sport on 28 July 2016.