John Key says he was coy about his intentions to resign as Prime Minister when asked by United States President Barack Obama at the APEC Summit in Peru last month.
Mr Key had already made up his mind, having told Deputy Prime Minister Bill English when he returned from a New York trip in September that he was "99 percent sure [he] was going to transition out of the job at the end of the year".
President Obama had seen political polling numbers from New Zealand, Mr Key explained to Paul Henry, and hit him up about it when they met for dinner.
"He could see we were really strong and he said to me something like, 'I assume you're going to run for a fourth term' and I said, 'Oh, look…I'm sort of mulling it over'.
Mr Key said he was trying to be as non-committal as possible.
"It was kind of a bit unfair to tell him because then it can feed through their system and goodness knows where all that goes.
"But when we played golf together he said to me at the time, 'How long are you going to stay?' And I said, 'I don't know but I'm not staying forever'."
The soon-to-be-former Prime Minister is now preparing to speak with another world figurehead, the Queen.
Buckingham Palace contacted his office on Monday, and Mr Key said he expects to speak to Her Majesty "today or tomorrow".
The Prime Minister says he was surprised he got choked up during this resignation announcement on Monday, thinking he would be "hunky dory".
He became emotional during the speech when talking about the sacrifices his family has made during the eight years he has been Prime Minister.
Mr Key says that because he'd written the speech and read it "plenty of times", he thought he'd be fine.
"I actually thought 'This will be hunky dory', you know? And then I got there and there was a little bit where I was starting to feel a bit emotional and I thought, 'Oh geez, hold it together'.
"I think it would be an odd person that didn't feel any emotion after everything that's happened in the last 15 years."
Reflecting on what he says will be "the biggest and best job I'll ever have", Mr Key says one of his highlights has been engaging with "everyday Kiwis".
"Very few people come up and call me names…as a general rule that didn't happen. People were really nice to me and they were always really generous."