I guess I should be straight with you from the beginning. I used to work for Rolls-Royce. When I was starting off in comedy I worked during the day at a Rolls dealership.

Once I had to deliver a Corniche convertible. I had to collect $30,000 in a paper bag from the guy buying it. But on the way back I stopped at a comedy club in Times Square.

My set went down well and I left for home pleased with myself. But two hours out, somewhere into Connecticut, I remembered I had left the paper bag with the $30,000 in it on the piano. The sense of horror was unimaginable.

That trip back to New York was one of the longest two hours of my life. I got to the club at two or three in the morning and a girl was singing on stage. I jumped up, saw the bag was still on the piano, grabbed it and apologised, saying I had forgotten my lunch. If the bag hadn’t been there I’d have only just got out of jail now.

It’s not the only drama I had while working for Rolls-Royce. I delivered a 1971 to a guy. Two days later he called, furious, saying the thing had burnt to the ground in his driveway. The official response was, “You must have been smoking.” He said, “I don’t smoke.”

Rolls-Royce has long been synonymous with the best. At the turn of the last century you’d open the bonnet and it would be “oooh” . . . you couldn’t hear it running. It was literally the best car in the world. My dad even called his Cadillac the Rolls-Royce of automobiles. And for the first half of the century they probably were the best, not just in terms of workmanship but engineering. They were the benchmark for which all other car makers strived.

Then after the war others started to catch up. The 1949 Cadillac had electric windows, a V8, air-conditioning and automatic transmission. That’s when Rolls-Royce started to lose ground. Jeez, even Ford marketed its LTD (a very ordinary car) as riding more quietly than a Rolls. And as recently as the 1990s you could buy a Lexus that would ride better than a Rolls.

In workmanship the Rolls-Royce has always stood out, but not in engineering. By the 1960s it was fix upon fix upon fix. It was as if the last days of old technology were always better than the first days of new technology.

I remember going to Rolls-Royce at Crewe. They’d proudly show me the place where the bomb fell through the roof during the war. And there, in a corner, boiling a kettle for a cup of tea while stitching leather for the Cloud or Corniche was Mrs Miggins, or whatever. She’d look up and say, “Hello deary”.

I have not been to Goodwood yet, but it took the buyout by BMW (and please, British readers, don’t shoot me for saying this) for things to change for the better. The Phantom by all reports (I have not driven it) is well engineered.

The 100EX, which I am lucky to be the first person outside Rolls-Royce or BMW to drive, is the experimental car that will form the basis for the Phantom convertible that comes out in a couple of years. In that respect it is a very important car for Rolls-Royce.

My first impressions of the 100EX were good. Rolls-Royce has made a remarkable car. The brushed aluminium hood is an amazing piece of automotive architecture . . . and it really is architecture. You feel as if you’re opening a door rather than lifting the hood. There’s a bit of ceremony involved.

The engine is 16 cylinders and has that Rolls- Royce emblem they’ve had since the beginning of time. It’s a marvellous piece of engineering. I bet you could do the coin test — put a nickel on its edge on the engine and it wouldn’t fall over.

I took it out on the streets of Beverly Hills and the chassis felt good. It is a luxury car and so it leans through corners more than a performance car would, but it seems to be a car built from a solid block of metal. It doesn’t rattle and shake like so many convertibles. The steering is nice and light. It certainly doesn’t feel like a heavy car. It is easy to drive.

I love English cars. I only have one Rolls-Royce. It’s a special with a Merlin Spitfire engine in. But I’d like to get a Rolls-Royce Silver Ghost. I have cars from most other English car makers.

What makes Rolls-Royce different is that it does the opposite of every other English car — it isolates you from the road. If I ran over a penny in my McLaren F1, the feeling with the road is so acute I could tell if it was heads or tails up. If I ran over the Royal Mint in this I wouldn’t be able to tell.

As I cruised Beverly Hills I imagined feeling a light thump. On closer inspection there is a Toyota Prius caught up in the wheel well. Not true but entirely plausible.

The engine is 9 litres. It’s like a steam locomotive. It’s like a massive hand is pushing you from the back. It must have 660 lb ft of torque. My first guess, in terms of power, was that it had about 525bhp. But it turns out that it has about 700bhp.

This car is fine round Beverly Hills but really it’s the sort of car you have to drive from one locked location to another locked location. Driving up the California coast in it would be wonderful but you can’t just leave it by the side of the street.

This car has a bling factor that’s enormous. I can see Hollywood falling for it and rap stars in particular. It is not so over the top you can’t appreciate it. It is not outrageous. The detailing is fine, though. Your eye can rest on any number of features and they are quite delicate, like the chrome air-conditioning and audio controls.

This is a wonderful car for not listening to the radio or CDs. In my business there is too much noise. I get in a car for quiet. The 100EX is so quiet that when I heard a clanging sound I was startled. It was only my watch. After some stop-start traffic the fan came on under the hood (sorry, bonnet). It was pretty noisy. This is a bespoke car so I trust they will sort that kind of thing out when they make the production one.

I was very fortunate that Marek, the designer of the 100EX, came round to my garage for inspiration for the car. That’s extremely flattering. We talked about the design of some of the cars I have; the nautical influence of some cars, the aircraft element of others.

Someone hooted me as we headed down Rodeo Drive. I felt like shouting, “Excuse me, am I crowding you?” It’s a big car but for goodness sake . . . Talking of pardoning me, I tried to find the horn and instead a voice came at me from the dashboard.

“Pardon me?” said the voice, sounding like the Queen was trapped somewhere behind the speedo. I’d set off the voice-activated command system. I asked her where the horn was. She didn’t reply. I guess she’ll get back to me.

One does feel tremendously successful driving this car. All the fittings are unique to it. There’s nothing cheap or plasticky. I think if you went from driving this for a week to driving a normal car, you would think, “Huh, this is a little teensy. It’s like the difference between high-definition TV and regular TV.”

Sometimes I take a chair and sit in my garage and just analyse a car, its lines, its beauty, its form. I’d feel very comfortable doing that with this car.

It’ll sell. It’ll sell huge. In terms of design it is brilliant, just brilliant. And the 16 cylinders are impressive. I’d want it for the 16 cylinders, for that front hood — that’s why I like it.

If this is the future of Rolls-Royce it is good news. Rolls-Royce started out being an engineer’s car and it is back being an engineer’s car. There was a day when the thumb was better than the micrometer and making the Flying Lady by hand was something to be proud of. No longer. Building by machine to exacting aircraft tolerances . . . now that’s impressive.

Luxury is not my main thing with a car. My big thing is performance. So luxury makes me feel a bit guilty. That’s the Scotsman in me. It’s the reason it’s the Tonight Show with Jay Leno not the Tonight Show Starring Jay Leno. If that was the title my mother, who’s Scottish, would say “Starring . . . who do think you are. You’ve got to put your name all over it . . .”

I am not the kind who pulls up in front of a hotel or restaurant. I’m the opposite. If I know my car is going to be parked somewhere, I’ll take a low-rent car or even rent a car. A car like the 100EX is meant to make a statement and I am not a statement-making kind of a person.

It is an amazing car but I don’t think I’ll get one when it hits production. Not because I used to work for Rolls-Royce but because I am not big on luxury. I sort of feel I don’t deserve one.

Call me odd but it’s just the way I feel. Blame my Scottish upbringing.

Vital statistics

Model 100EX — full name to be confirmed. Leno drove a prototype. The production convertible will have different specifications, including a 12-cylinder 6.75 litre engine
Engine 16 cylinder V formation, 9 litres
Power 700bhp (estimated)
Torque 660 lb ft (estimated)
Transmission Six-speed automatic
Fuel n/a
Acceleration 0-60: less than 6sec (estimated)
Top speed 150mph plus (estimated)
Price More than £250,000