Atherton’s Giant Reign used the Lisbon Downtown course – made famous by the annual Red Bull race – and the car followed a similar length course but without the stairs.
The segment took one and a half days to film. Atherton is remaining tight-lipped on whether the Giant Reigned in Portugal.
BBC2’s Top Gear is watched by 5.8 million viewers in the UK and more than 200 million worldwide on BBC Worldwide.