Whispers that the trio were at the Autódromo first emerged on Wednesday and spread like wildfire after presenter Clarkson posted an image of the cast and crew on the track on his Twitter account.

A note accompanying the photo says: “With a skeleton crew, filming for Amazon Prime’s new motoring programme has begun.”

Earlier that day Clarkson hinted work on the new show could be about to start by posting a picture of a sunrise, telling his followers: “Dawn. On a very special day.”

James May and Richard Hammond also dropped hints on their respective accounts, with Hammond saying: “The band is back together and it feels brilliant.”

May alluded not only to his job but also to the cars they were posing with, captioning his photo of a McLaren: “Great first day at work. I can’t stop staring.”

The supercars in the photos have been identified as being a Ferrari LaFerrari, a McLaren P1 and a Porsche 918 Spyder.

The Portugal News understands that the filming was meant to be a top-secret affair and their visit supposedly highly confidential.

Addressing their presence in the Algarve, a source from Portimão Council, the municipality in which the racetrack is located, said once the footage airs, in terms of tourism promotion it will have “a big impact on the outbound market” and is “significant action for us as a destination.”

The new show, said to be called ‘Gear Knobs’, is due to air in 2016 on the Amazon Prime streaming service.