As with any contact sport, stand-up comedy is best enjoyed live and up close. Watched from afar—on television or a computer, or even from the upper balconies of a theater—the spectator misses the game within the game: the look in a comedian’s eyes when a joke lands. The wide-eyed, almost primitive shock when a joke misses. The quick recalibration with gesture or movement to provide just that exact amount of spin to properly hit a punch line smack dab in the sweet spot. There’s sweat. There’s glory. There’s a connection between performer and witness that’s visceral. Both sides leave exhausted, either through joy or, ever so often, embarrassment.

Now take a stand-up who’s not merely good but someone who stands on the rarified pinnacle of the comedic mountain. A comedian so great that even other top comedians, not necessarily known for their easy accolades, claim him as being one of the very best, perhaps ever. And there stands 57-year-old Brian Regan.

On Saturday night, Regan was the headliner at Comedy Central’s first-ever live broadcast, a stand-up event at Radio City Music Hall. Called “an absolute master” by Bill Burr, Regan has been a professional stand-up since 1980. Through an unrelenting, never-ending schedule (and with the benefit of 28 performances on Late Show with David Letterman), he has moved into the pantheon of the few: auditoriums, arenas, and, yes, theatres spelled the fancy British way.

Perhaps even more impressively, Regan works clean, and always has. There is no blue material in his sets. Subjects range from batting away cobwebs like a maniac to an astronaut making small talk at a dinner party to the ubiquitousness of cranberries in fruit drinks. The material never goes bad, as it’s never tethered to topical references. It’s observational but never cloying. To say that it’s just “clean”—as if that’s an accomplishment in and of itself—doesn’t do it justice. It’s great and has remained consistently so for the past three decades.

Backstage at Radio City, I had the opportunity to watch Brian from a different angle, just offstage left, the closest I’ll ever come to know—many degrees removed—as to what it’s like to stand in front of a sold-out show of 6,000, and many hundreds of thousands more at home. I felt oddly vulnerable, almost as if I were standing just behind a pitcher’s mound during a big game.

What follows are a few of my observations. I’ve also provided, in parentheses and italics, the responses Brian so kindly gave me before and after the show:

There is no backstage chaos like the kind one would see at a rock show. There are no roadies. There is no partying. If there are groupies, they blend in very well. Ten minutes before the start of his act, Brian enters the backstage area, toward the back where it’s dark, and paces. It almost looks as if he’s going through the entire routine in his head. He isn’t smiling. (“I always pace by myself before my shows. It’s a good way to zone in on my what I’m going to do. The other night, I had a few transitions from subject to subject, that I was a little shaky on, so I was reviewing in my brain the links to use to make the transitions. There were four or five times when I was in a bit, not knowing what the next bit was, so the pre-show brain review helped me out. ‘Oh, yeah! Now I talk about being a dishwasher.’ ”)

As the introduction is announced, Brian bounces and sways like a boxer about to enter the ring. He downs an entire bottle of water. He looks very alone. Yet he also appears confident and loose. How nervous is he? Does this particular show mean more than the 86 others he’ll perform in 2015? Regardless, when his name is announced, he charges out onto the stage, without hesitation. He looks to be at home. (“I’ve never done a live televised special. I do live shows every night in front of those audiences, so it’s not freaking me out. But certainly there’s an extra layer of excitement because of the magnitude of this.”)