Prince Charles today called Prince Harry his 'darling boy' after his son told him he 'picks his brains more now than ever' during a radio interview.
The 33-year-old was guest editing Radio 4's Today programme and affectionately called his father 'pa' and thanked him for 'allowing' him to interview him for the show, the Daily Mail reported.
And during the four-minute chat, the Prince of Wales said it was 'amazing' that he had been listening to him regarding climate change.
The pair started talking about the planet and the 69-year-old joked that people are finally waking up to his 'dotty' opinions about the environment.
When asked by his son to pick one issue to focus on, Charles said over the years there have been a 'whole lot' of things he has tried to focus on that he thought needed attention.
He said: "Not everyone else did, but maybe now some years later they are beginning to realise that what I was trying to say may not have been as dotty as they thought.
"The issue really which has to go on being focused on, big time I think, is this one around the whole issue of climate change.
"Which is now, whether we like it or not, is the biggest threat multiplier we face because what is happening now is what I was dreading.
"Which is we are having to deal all the time with the symptoms that are springing up all round the world, and they are diverting us off down all these different channels to try and deal with ghastly conflicts and humanitarian and natural disasters, and goodness knows what else.
"But at the root of it all, much of it, is climate change which is causing untold horrors in different parts of the world."
When he started the interview, Prince Harry referred to his father as 'pa' and said it was 'very nice' to see him.
He later asked him: "Moving on, I know the two of us could end up talking about this for hours and hours and hours of which we always do but not with a microphone in front of us.
"But do you feel optimistic about the future, for the world that William, myself, your grandchildren and everyone else out there is going to inherit."
His father replied: "Well my dear boy if I must say so, the fact you're saying this, gives me enormous optimism. I haven't obviously put you off when banging on all these years.
"Because if you think that, that is really encouraging. What I've tried to do all these years is to make sure that I can ensure that you and that your children, my grandchildren, also everyone else's grandchildren, have a world fit to live in."
Harry later told him: "I totally see it and I totally understand it because of all these years of conversations that we've been having and I do end up picking your brains more now than I ever have done."
His father added: "Well darling boy it makes me very proud to think that you understand."
Harry then joked: "And that I'm listening?"
"Well that's even more amazing", his father said.
When Barack met Harry
Former US president Barack Obama warned against using social media in a divisive way during his interview with Prince Harry.
Mr Obama, 56, did not mention his successor in the White House by name, but many will see the comments as a thinly veiled rebuke aimed at Donald Trump.
During the interview, Mr Obama said there was a danger of people becoming stuck in their biases due to social media use.
The ex-president said: "The question, I think, really has to do with, how do we harness this technology in a way that allows a multiplicity of voices, allows a diversity of views, but doesn't lead to a Balkanisation of our society, but rather continues to promote ways of finding common ground?
"And, I'm not sure government can legislate that, but what I do believe is that all of us in leadership have to find ways in which we can recreate a common space on the internet.
"One of the dangers of the internet is that people can have entirely different realities. They can be just cocooned in information that reinforces their current biases."
President Trump has drawn widespread criticism for the way he uses Twitter to attack opponents, and condemn what he brands 'fake news'.
During the same interview, Obama said he prefers Prince William over his brother while he was getting grilled by the prince.
At the end of the 40-minute chat, the fifth in line to the throne fired questions at the 56-year-old and asked him who he preferred, 'William or Harry'.
He joked: "William, right now."
Harry also asked him which popular US television show he preferred out of legal drama Suits - the programme which his fiancee Meghan Markle made her name - or the Good Wife.
And to his delight he answered: "Suits, obviously" with Harry replying: "Great, great, great answer."
During the 'lightning round' of questions, The former president declined to say whether he wears boxers or briefs.
But he was willing to say he prefers Aretha Franklin to Tina Turner - "Aretha is the best," he said of the Queen of Soul - and favours retired basketball star Michael Jordan over current star LeBron James.
He also said he prefers 'The Queen' to the band Queen to which Harry said: "Another great answer."
Obama also told the prince he felt serene on the day he left the White House despite feeling important work remained unfinished.
He said it was 'hugely liberating' to be able to set his own agenda in the morning and to have the time to talk with his wife, Michelle, now that he is no longer president.
Both men said the interview, recorded in Canada in September, was Obama's first since leaving the presidency in January.
Obama, speaking about his eight years in the Oval Office, said: "I miss the work itself because it was fascinating."
Obama also revealed he is 'obsessed' with helping to train the next generation of leaders and said the world is in many ways healthier and wealthier than it has ever been.
At the end of the show, Harry would not say whether Obama will be invited to his May wedding to American actress Meghan Markle, saying the guest list hadn't been drawn up yet.