The BBC Radio 4 Today programme shook things up this morning with a guest presenter, as Prince Harry took to the airwaves.
This is what Prince Harry spoke to his guests about:
The ex-world leader said one of the things he misses most about his old job is "the fact that I didn’t used to experience traffic". "I used to cause traffic - much to the consternation of any place that I was visiting," he quipped.
On the subjects of fake news, trolling and cyber bullying, Obama said: "One of the dangers of the internet is that people can have entirely different realities. They can be just cocooned in information that re enforces their current biases. One of the things that I think, I discovered even back in 2007/2008 is a good way of fighting against that is making sure that online communities don’t just stay online. That they move offline.
"And what I mean by that is that I think social media is a really powerful tool for people of common interests to convene and get to know each other and connect but then it is important for them to get offline, meet in the pub. Meet at a place of worship, meet in a neighbourhood and get to know each other because the truth is that on the internet everything is simplified and when you meet people face to face it turns out they are complicated."
The former US President also sounded a note of optimism about the state of the world looking into 2018.
"All the problems that we face are solvable. Despite all the terrible news that you see. Despite all the genuine cruelty and pain and hardship that people are experiencing around the world at any given moment of any given day," he said.
If you had to choose a moment in human history in which you want to be born and you didn’t know ahead of time if you were going to be Prince Harry or Barack Obama or a small child in rural Africa or India you’d choose today because the fact is that the world is healthier, wealthier, better educated, more tolerant, more sophisticated and less violent than just about any time in human history.
Prince Harry spoke to his father about climate change, a favourite topic of the Prince of Wales, who admitted he had "probably bored (Harry) to tears for so many years" on that very subject.
Climate change "whether we like it or not is the biggest threat multiplier we face", according to Prince Charles.
"Because what’s happening now is what I was dreading which is that we are having to deal all the time with the symptoms that are springing up all round the world," he added.
"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 and of course we sit here in this part of the world so often unaware of what is happening in Africa or the Far East.
"It’s a miracle, I think, that everything is here. That’s why I have gone on about this because, to me, the unutterable tragedy, the inexcusable one, would be if we destroyed this quite remarkable planet and ecosystem. Because we depend on nature and the ecosystems for our entire survival. Nature is our sustainer."
Hassabis, the founder of AI company DeepMind, explained to Prince Harry and listeners what his firm's "very ambitious mission statement" is all about.
What we mean by solving intelligence is we are trying to create general purpose learning machines. So we’re trying to create systems that are capable of learning for themselves how to solve complex problems.
"And we’re kind of inspired by human intelligence and the way the brain works. So the algorithms that we build are neuroscience inspired and we’re trying to mimic some of the ways that the brain solves these complex problems. And what we hope is that if we solve intelligence and artificial intelligence in this very general way, we will be able to apply this technology to really wide range of domains."
Hassabis said government regulators and the media are beginning to get to grips with AI and its potential: "I think that people have to realise technology isn’t neutral and when we create that technology it’s amazing the impact and the scale it can have because it’s digital and it’s easy to scale. But I think that people have started realising that we have to think ahead of time about problems that may collateral problems that you didn’t necessarily realise when you were starting to make the technology but you need to think harder about that at the beginning as you are making a technology not waiting for the problems to appear and then trying to run and catch up."
He also told the prince why he's keeping DeepMind in London.
I’m a proud born and bred Londoner I love London and Britain and I think that I have always believed that we have top talent here.
"We have world leading universities and it just requires I think the ambition and the drive to actually really try and create a deep technology company like Deepmind. And I always felt it could be done in London. But I was told at the beginning when we were starting up that we were crazy and that we should go to Silicon Valley and that that was the only place that you could build these types of companies."