Tied-up in jokes

to do Letterman than The Tonight Show.

“For a long time, I didn’t do Carson because I thought it was cool just to do Dave,” he says.

“And then finally there was a rumour in late ’87 that Johnny might leave and then I thought, ‘Well, I’m an idiot. I’m just afraid of it. That’s why I’m not doing it.’ So I did both. But Dave was always the show for me to do and it was important to score.

“And no matter where you were in your career, you felt really, really, really proud of yourself and happy if you killed on Letterman.”

Robert “Morty” Morton, Letterman’s longtime executive producer, could see Letterman mature over the years.

“It started with his way of opening up his conversations with favourite guests like Bill Murray, Steve Martin and Tom Hanks,” says Morton.

“When you asked Tom Hanks a question of when he worked as a bell hop, he’ll tell the story about bending the shaft on golf clubs.

“The seismic shift was when Letterman realized ‘I have a more powerful voice than just being a jokester. I have a very strong voice of a generation.’

“When he came back (after) 9-11, he was bold enough and daring enough and didn’t need the reinforcement of laughter to get out a message. I think he took on a new responsibility.”

When Letterman hosted his final Late Show in 2015, some thought he would step away from the spotlight.

Jimmie Walker, one of his oldest comedy friends, admits he has been surprised by Letterman’s decision to do everything from a new show on Netflix to appearing at public events.

“I think all of us are a little shocked that he’s doing as much as he’s doing,” says Walker, who hired Letterman in the ’70s to serve on a writing staff that included Leno, Louie Anderson and Byron Allen.

“I expected even less than what Johnny Carson did. That he would be totally insular. Nothing. I expected him to be what Cosby’s doing now. Just not heard from again.”