The Grand Tour stars on pirate treasure, cycle lanes and electric cars

Jeremy Clarkson, Richard Hammond and James May attempt to find pirate treasure in their new special, The Grand Tour presents: A Massive Hunt.

The trio head to Madagascar for their latest Amazon film, with little more than a car each and a historical treasure map.

The challenge starts with the tale of an 18th Century pirate known as La Buse (The Buzzard). Legend has it that, before he died, he buried his treasure - worth £100m in today's money - somewhere in the Seychelles.

When he was finally captured and executed in 1730, he hurled a piece of parchment into the crowd, shouting: "My treasure for he who can understand!"

The parchment contained a 17-line cryptogram which apparently revealed where his treasure was buried... but only if someone was able to decipher it.

Many have tried and failed over the centuries to locate the loot. We've been speaking to Clarkson, Hammond and May about their own hunt (and a few other things in between).

In the course of the 90-minute special, May makes a decent and serious attempt to crack the codes. Which raises the question, did the team ever think they might actually discover the treasure?

"Yes! I did all along," says the lovably enthusiastic Hammond. "I'm a massive fan of all of that stuff. It's historical fact that a lot of these people did exist, as did their treasure. So you never know, there was a chance."

Executive producer Andy Wilman has a slightly different reaction when we put the same question to him.

"Are you mentally deranged?" he asks us, which we'll take as a no.

"I'll tell you what it did do, it made you a kid again. I'm getting paid to hunt for buried treasure, like I'm seven. It's one of those situations where your tongue has got to come through your cheek. So the viewer can see [we know] that this is nonsense. But you go with it because of the journey, it's a great adventure to go on."

You might have thought that the team would have a hard time topping the name of last year's special, The Grand Tour presents: Seamen, which saw the trio swap cars for boats. But they've outdone themselves here.

So whose idea was The Grand Tour presents: A Massive Hunt?

"You won't believe me when I tell you, but it was the people we work for," reveals Wilman. "Old big corporate Amazon.

"We were batting titles backwards and forwards and it was like 'best one wins'. And then I got a text from their head of marketing and I was like, 'oh yeah, game over, our work is done now'."

Perhaps the most gripping section of the new special comes when the trio have to find their way along a road in Madagascar - although the word "road" is being rather generous.

"It's extraordinary that it's actually marked on a map as a thing you can drive a vehicle on," says a bewildered Clarkson. "I'm not surprised the Madagascans threw the French out if that was their idea of a road, because it just isn't one."

May admits: "In terms of trying to get your car to the end, we honestly thought near the beginning of filming that we simply weren't going to be able to do it.

"I've never driven on a road that difficult to simply negotiate. It's worse than the centre of Swindon, with all those mini roundabouts. You could spend the rest of your life there if you're not careful."

You may remember Clarkson publicly acknowledged climate change for the first time in last year's special, after the awful conditions the team witnessed in Cambodia. But that doesn't mean he's about to change his behaviour.

"I've just ordered a new Bentley, with a V8 engine, so that's where I stand," he says. "[Hammond and May] both have electric cars now but I'm carbon offsetting them."

He refers to recent reports of "appalling" child slavery in the Democratic Republic of Congo, after the huge surge in demand for cobalt - a critical metal for electric car batteries.

"They're also very expensive and completely impractical and have the personality of a vacuum cleaner but if that's what you like, help yourself to an electric car."

...because it sounds like he had quite a traumatic experience travelling to the press launch.

"It took me three hours to get to where I am this morning, because the Mayor of London is an imbecile," he says with his usual tact. "He's just turned the whole damn city into a cycle lane.

"I don't mind one or two cycle lanes where it's convenient but he's put one in the Euston underpass. I mean, the man's a maniac and must be stopped."

Clarkson has always enjoyed being provocative with the things he says, but we thought we'd better put these comments to the Mayor of London.

A spokesman for Sadiq Khan told us: "London is facing an air quality crisis which is causing thousands of deaths per year and exacerbating the physical effects of Covid-19. Half of toxic emissions in the city are caused by road transport.

"These policies are about saving lives and Sadiq makes no apologies for the temporary emergency measures he has put in place to encourage the huge increase in cycling we've seen since the pandemic began which is also enabling social distancing on public transport. We mustn't get through one public health crisis only to face another caused by congestion and toxic air pollution."

After the special is released next month, James May hopes it will prompt renewed interest with the public in finding the treasure.

"The coded message is available in various books and online, and there are many ways of reading it and interpreting it, as I hope I showed, but if other people want to have a crack at it, I think that would be very interesting," he says.

"Even if you did manage to translate it, it would be in an old language which we're not very familiar with, so getting all the way through to what it actually means is going to require massive research knowledge and interpretative skills. But even if it's just for a bit of fun, I hope people still have a go at it, it's quite absorbing actually."

Wilman describes having to edit the Madagascar film over Zoom as "a living hell".

Lockdown also meant the team had to get creative when they began filming their next special, and find something to do within the UK.

"We were trying to think of different options, and where we ended up was we just shot one recently up in Scotland, a kind of mini coronavirus special, which will be 60-odd minutes rather than 90," Wilman explains

But how much longer will the trio continue doing The Grand Tour? They've been with Amazon since 2015, and were on Top Gear for 13 years before that.

"I am aware of ageing, and perhaps the need to grow up, now I'm in the second half of my 50s," says May. "But I think we'll do it for a bit yet because, to be honest, people want us to, and it would be wrong of us to disappoint them.

"But eventually one of us is going to snap, yes. Probably me. I'm quite fragile, really."

Wilman explains that he and the trio all got individual solo deals when they signed with Amazon, which meant each was given their own series in addition to working on The Grand Tour.

As a result, Clarkson has done a farming series, Hammond has a forthcoming survivalist show, while James May recently launched his own cookery programme. "I've still got one to do," Wilman says, although adds that he'll remain behind the scenes rather than on screen.

"We'd like to do two [Grand Tour specials] a year, that was the plan. We've still got two to do, on our current contract. And that's about right, two allows us to do other things, and keep Grand Tour going."

The Grand Tour presents: A Massive Hunt will launch Friday 18 December on Amazon Prime Video.