Truly, it was a privilege to work with Leno, an icon of my generation. Seriously. I was over the moon. Which is why that behind-the-scenes horror that ended up happening was so mortifying. It's also an object lesson in how, when you’re dealing with cars, things can wrong quickly.

I was there to talk about the history of the GT40, which figures prominently in a book I wrote called Go Like Hell . Leno was there to provide the jokes, the cameras, the platform. As it turned out, the episode also featured a great interview with Mario Andretti .

The scene: One day last summer, I arrived on the show's set to appear on a segment. Here was the man himself, in a nondescript parking lot in Los Angeles, with a 1967 Ford GT40 Mk III borrowed from the Petersen Automotive Museum. Leno was wearing a plain light-blue work shirt, as he so often does. The car was as rare a beast as ever prowled the backlots of LA. To see one driving down the road would be like seeing Elvis himself in the flesh, standing on line at the pharmacy to buy Gas-X pills. Only seven Mk III’s were ever built, and only four of them left-hand-drive—like the one Jay and I would be filming in on this day.

So we were in Leno’s garage, arranging to shoot the final piece of my segment. I was in the GT40’s passenger seat. Leno was getting in the driver's side. It is a very small automobile, standing just 40 inches off the ground, and he’s a big guy. He was having trouble climbing into the driver’s seat. GT40 fans know that the doors are shaped oddly. The top of the door cuts deep into the roof. Leno had reached his hand across the roof to where the passenger side door meets the roof, even though he was climbing into the car’s driver’s seat. Think about it: How could I know, sitting in the passenger seat, that his hand was in my door well, when he was standing on the other side of the car, getting into the driver’s seat? Anyway…

I remember saying to myself as I shut the door: This is an antique car! Shut the door gently. But not too gently, or the door latch won’t catch. I pulled the door closed and heard a THUD. I knew instantly what had happened, even before I heard this world-famous TV icon bark loudly in pain. I had never been so instantly unnerved. As I write this, the story still makes beads of sweat curl down my forehead, just thinking about it. As I recall, the conversation went like this:

“Oh shit!” I said. “Sorry. Oh shit!”

We both looked at his hand. He said, with amazing politeness, “I didn’t know you were going to slam the door shut on my hand.”

We both looked at his hand. Now, the hand is a complicated piece of machinery. It has about 30 little bones, 29 major joints, at least 123 ligaments, 48 nerves, and 30 arteries. All this stuff is small and complicated to fix if busted. I’ve seen broken hands before; they usually require surgery. Here I am sitting in a GT40 thinking: How is Jay Leno going to film his brand new TV show on a major network, if he needs surgery to repair his hand? And how is he going to film a car show with a great big cast on his hand? Then I’m thinking: What is going to happen to A.J. Baime!? You destroyed this TV show, you loser! You are about to become the laughing stock of the motoring world! All of this is going through my head in the handful of seconds after I slammed his digits in a door.

Turns out, of course, he was fine. I followed him around for the next hour, my eyes focused on his hand, to make sure he was okay. And he was. Even when it was time for me to split, I approached him with my hand out, to see if his right hand was in too much pain for a hand shake. Jay was offering his hugely warm smile, and shook my hand with gusto. I dodged a bullet. He dodged an even bigger one. I haven’t spoken to him since but if you’re reading this, Mr. Leno—sorry for almost ruining your TV show. And thanks again for having me.