The Grand Tour's executive producer Andy Wilman introduces the final special of season three: "Without a shadow of a doubt the best has been saved till last"

Of all the types of shows we make, The Grand Tour specials are far and away, hands down, no arguments, the hardest.

Not just the hardest to shoot, but more importantly the hardest in which to keep delivering the goods and satisfying expectations.

That's why we normally just shoot one per series. But for series three, because we clearly struggle with basic maths, we've somehow ended up shooting four.

There's been the Colombia expedition, the RV holiday in Nevada, the road trip across Georgia and Azerbaijan, and now finally, this coming week, we give you the Mongolia Special, and without a shadow of a doubt the best has been saved till last.

The premise is as simple as it is cruel: our three intrepid halfwits are dropped in the middle of the vast wilderness of Mongolia, hundreds of miles from any kind of civilisation, with just the shirts on their backs. Then, three crates are parachuted out of a helicopter. Inside the crates are a stash of car components and a message from Mr Wilman (how much do I love my job on days like these) telling them that in order to reach civilisation, they must build a vehicle from the components and somehow navigate their way through the wilderness.

This last part is extra hard because they have no phone signal and the map Mr Wilman has provided is straight out of the Winnie the Pooh school of cartography. Just to make things worse, they only have food and water for seven days and there is no instruction manual for how to build the car. And even if there was a manual, Jeremy would be of no help, on account of him having the mechanical skills of a kitten.

What follows over the resulting 90 minute show is, in my opinion, which is a good opinion, not just the best Special of the series but one of the best we have done in many a year.

You remember those MTV Unplugged albums, the ones that proved a great song remains great even when it's simplified to its basic components? For me this show is one of those. Everything is stripped back; there are none of the contrivances we can sometimes be guilty of. You just get an endeavour that is immense and a journey that is properly, properly brutal.

Before they can go anywhere though the vehicle must be built - a task which falls to Richard and James. Fortunately both of them have always been good with a spanner, but unfortunately one of them likes to take half a day doing up a nut whilst the other likes to slam something together as quickly as possible so he can get on with having a crash in it. Despite their differences though, a machine of Mad Max-ian provenance does eventually come together and the three of them then begin their epic odyssey to find a shower, a bog and a drink.

The trek to civilisation is without doubt one of the toughest and most arduous Richard, James and Jeremy have ever undertaken. As jaw dropping as the Mongolian landscape may be - and My God is it ever - its terrain throws up immense challenges and obstacles, and if you've been following us these last 18 years, you'll know those three are hardly poster boys for middle aged fitness.

And yet through all the pain and the struggle (actually, probably because of the pain and the struggle), they are absolutely on their A game when it comes to delivering the wit and the laughs. I know I should probably be leaving it up to the viewer to make that kind of judgment, but I honestly believe that, stoked up by their surroundings,  and having only their dysfunctional friendship to fall back on when times get really tough, their banter in Mongolia is at its brilliant best.

And finally there's the fourth star of this show: the car, which will without doubt join the pantheon of greats alongside Oliver, the Indestructible Toyota Hilux and the Hammerhead Eagle i-Thrust.

As you've probably guessed, I'm very proud of this show, and this comes from a man whose glass is not only half empty, but sees that what's in it is not even what he ordered. But the combination of Mongolia, those three and the machine they build to cross it is the absolute essence of what we're put in front of you to do.

After the Mongolia adventure there will be one more conventional show, the finale for this series. Then we're pulling down the curtain on the studio-based episodes so that we can just concentrate on big Specials. If Mongolia is anything to go by, we'll be okay.

The Grand Tour Mongolia special will be available on Prime Video from Friday 5th April

Read more: The Grand Tour season four will only feature big road trips