Andy Wilman, the executive producer of Top Gear and the man responsible for much of the show's style and humour, has quit the program following the sacking of his close friend Jeremy Clarkson.

In a leaked email obtained by motoring blog site Jalopnik, Wilman thanked staff and called Top Gear "one of the most iconic programs in TV history" that was "beautiful to look at and beautiful to listen to".

"Well, at least we left 'em wanting more," he writes. "And that alone, when you think about it, is quite an achievement for a show that started 13 years ago.

"We had a lot of laughs, we had a lot of tiffs. We went to amazing places and we went to some shitholes. We nearly killed a presenter, we had to run for the border."

Clarkson, who was sacked after allegedly assaulting a Top Gear producer, first met Wilman when they were both students at Repton School, a $20,000-a-term private boarding school in Derbyshire.

Top Gear mythology has it that the pair cooked up the new format for the show in 2002 while sitting in the pub.

But while Wilman's departure is undeniably a huge blow for the BBC and its Top Gear cash cow, which earns up to £150 million ($290 million) worldwide for the corporation, he gave some hope to fans in his email.

"For those of you who still rely on it for work, don't worry, because the BBC will make sure the show continues," he writes. "Our stint as guardians of Top Gear was a good one, but we were only part of the show's history, not the whole of it. Those two words are bigger than us."

Wilman's decision to pull the pin follows reports that co-hosts James May and Richard Hammond are also considering quitting.

Late last week, another key member of the Top Gear team also headed for the door. Richard Porter, the show's long-time script editor, announced via Twitter that he was leaving, adding further credence to the view that Top Gear will have to be rebuilt from the ground up if the BBC is hoping to resurrect the series.

Porter, R. Scrpt ed. 13 years, 22 series, 175 programmes. Hon. dis. — Sniff Petrol (@sniffpetrol) March 26, 2015

Meanwhile, thousands of fans who have bought tickets for the Top Gear Festival slated for April 18 and 19 at Sydney's Motorsport Park are still waiting to find out the fate of the event.

Many have taken to social media to vent their anger, with some calling for refunds if the show was to go ahead without Clarkson.

A decision from BBC Worldwide is expected by the end of the week.

Full text of Andy Wilman's email

Well, at least we left 'em wanting more. And that alone, when you think about it, is quite an achievement for a show that started 13 years ago. I know none of us wanted it to end this way, but for a moment I'd like us to look back and think about just what an incredible thing you all had a hand in creating. When Jane Root gave us the green light in 2002, the brief was to reinvigorate a car show and get an audience of three million. What you all ended up making was one of the most iconic programmes in TV history, a show about cars that went global, won countless awards, was devoured by non car fans and ended up in the Guinness Book of Records.

We had a lot of laughs, we had a lot of tiffs. We went to amazing places and we went to some shitholes. We nearly killed a presenter, we had to run for the border. We started off with whoever we could get in the Reasonably Priced Car, and ended up with Tom Cruise. Throughout all this we made television that was beautiful to look at and beautiful to listen to. The work ethic never slipped, the desire for everyone in this dysfunctional family to do right by the show never faltered. Jeremy, Richard and James, as the visible tip of the iceberg, got most of the attention and praise, but you all in your own fields had such an immense hand in weaving this unforgettable tapestry. I would love to single out everybody by name to thank them for what they did, but it's impossible and I'd forget someone I shouldn't have and that would be crap, so I'll just say Jim, I'm sorry we never got a bear to drive an automatic.

For those of you who still rely on it for work, don't worry, because the BBC will make sure the show continues. Our stint as guardians of Top Gear was a good one, but we were only part of the show's history, not the whole of it. Those two words are bigger than us.

Anyway, when you're feeling low in your working day at any point, look around at some of the crap on TV, then have a think about Top Gear, 2002- 2015, and say to yourself: "I made that."

A big, big, big thank you, which will never be enough.

Andy.

Follow Entertainment on Twitter