Chat show host Michael Parkinson has revealed the questions his guests have told him they would rather not be asked - and admitted that he has sometimes forgotten their names.
After interviewing more than 1,000 celebrities in 36 years, Parkinson is now filming his final series.
The 72-year-old told the Radio Times magazine: "Mine is the last of the classic interview-based chat shows, the rest of them now are just comedy shows.
"Nothing wrong with that, but it's not what I do. So this is it. I'm done... I'm bound to be a bit sad as I walk on for that very last time."
"There have been times when I've looked at the person I'm interviewing, and they're chatting away, and I can't for the life of me remember their name.
"It happened with John Wayne. I simply couldn't think of his name, so I stared at my crib sheet and it said 'Duke', which was his nickname, of course, but that didn't do me much good.
"I thought: 'well it's not Duke Ellington, and it's not the Duke of Plaza Toro. Who is it?' And it just wouldn't come to me."
Parkinson also revealed that he could not present Muhammad Ali, who suffers from Parkinson's disease, with an award after interviewing the boxing legend four times.
"I couldn't bear the idea of having to look into those dead eyes, not after meeting him when he was the most glorious athlete I'd ever seen," he said.
He revealed some of the questions his guests did not want to be asked: "Woody Allen said he didn't want to talk about the relationship he was having with his stepdaughter.
"So I had to point out to him that it had affected his career in a major way, that Middle America just wouldn't buy him after that, so I was going to have to ask him about it.
"He agreed to talk about it in that context, though he was still pretty reluctant.
"Rex Harrison told me that he wouldn't talk about his ex-wives, and I said: 'Rex, you've been married eight times, that's going to leave a pretty big gap'.
"He said: 'Yes, I suppose you're right, dear boy'."
The chat show host had a famously difficult interview with Meg Ryan.
He said of the Hollywood star: "She was just rude. She came on after Trinny and Susannah, who'd been talking about power-dressing, so I asked her what she thought, and she said: 'Oh, did you do a piece about fashion? I didn't know that'.
"Of course she knew, she been watching backstage before she came on. I thought: 'You cow'. I mean, what can you do with someone like that?"
Parkinson began his BBC1 chat show in 1971 and switched to ITV in 2004.