Now we know why the Ferrari driver was hanging out with Hammond and May last summer.

The third and final studio series of The Grand Tour has just wrapped up with a tear-jerking finale in which Jeremy Clarkson, Richard Hammond, and James May looked back on their 16 years working together.

One thing they didn't look back on was a scene filmed with Sebastian Vettel last year. Hammond and May were photographed filming with the four-time Formula 1 world champion at a Shell petrol station in the days after last year's British Grand Prix.

What was being filmed featured the hosts' personal cars – Hammond's 1963 Opel Kadett (named Oliver) from the 2007 Top Gear special filmed in Botswana and James May's bright orange Ferrari 458 Speciale.

However, the latest series of the hit Amazon Prime show didn't once show any of the segment filmed that day. So what happened?

The Grand Tour Vettel Shell advert screenshot

Well, what we actually saw being filmed on that day was a mini-film for Shell. The film, called The Perfect Drive features Hammond in 'Oliver' and May in his Ferrari debating which is the best car to drive for pleasure. The pair pull over at a petrol station to continue their debate, where they conveniently bump into Vettel, who them serves as a referee as both put forward their case as tho why their car in better than the others.

You can check out The Perfect Drive here.

The Grand Tour Vettel Shell advert screenshot

The recent final episode of The Grand Tour's studio run focused on the impending end of production for the Ford Mondeo.

"It's very sad, and it's not the only British motoring institution that's coming to an end. We are," Clarkson said at the end of the episode. "This is not just the last in the series, the show as you know it is actually ending – with the track, audience, us three, and really badly-fitting jackets every week. This is the last one."

The upcoming fourth season of the show was confirmed late last year amid rumours of the show's demise. The fourth season will comprise of road trip special episodes, such as the Colombia and Mongolia films featured in Season Three.