Former U.S. President Barack Obama says young people wanting to make change need to look up from their phones and internet cafe sex videosget out into their community, in what he says is his first interview since he left office in January.

He also warned that social media was causing people to have entirely different realities, and said leaders need to do more to ensure a way to find a common space on the internet -- a possible dig at tweeter-in-chief Donald Trump, and his screeds that many people find polarising.

Obama gave his much-anticipated interview to none other than Britain's most famous fiancé, Prince Harry, who was a guest editor on BBC Radio 4's Todayprogramme on Wednesday.

Obama spoke about what it's like after being president, his thoughts on millennials, and if he preferred Suitsor The Good Wife(just take a guess, considering that Prince Harry is newly engaged to Suitsactress Meghan Markle...)

The two clearly have a good rapport and Prince Harry prepared some interesting questions. At the beginning of the interview, he asks probably what we were all thinking... just what was going through Obama's mind during Trump's inauguration?

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"The sense that there was a completion, and we [Michelle and Barack] had done the work in a way that preserved our integrity and left us whole, and that we hadn't fundamentally changed, I think was a satisfying feeling. That was mixed with all the work that was still undone, and concerns about how the country moves forward. But overall there was a serenity there, more than I would've expected," Obama said.

Obama said that he appreciates having the time to think about longer-term projects now that he's not president -- and being able to have leisurely mornings.

Discussion about social media also featured prominently in the interview. Both Obama and Prince Harry are well-known for their use of social media. This generation of the royal family, in particular, has used it to highlight causes like their Heads Together campaign for mental health.

Yet Obama warned of the discord that it's caused society, and insisted that as a former constitutional lawyer he'd never want to censor it. He never mentioned Trump by name but it's hard not to imagine that he's talking about him.

“The question is: how do we harness this technology that allows a multiplicity of voices, a diversity of views but does not lead to a Balkanisation of our society but rather continues to promote ways of finding common ground?

“All of us in leadership have to find ways to recreate a common space on the internet. One of the dangers of the internet is people can have entirely different realities. They can be just cocooned in information that reinforces their current biases,” he said.

Obama and Prince Harry also warned that just taking action online -- slacktivism -- isn't the way to bring change.

"A good way of fighting against that is making sure that online communities don't just stay online, that they move offline. 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's important for them to get offline, meet at the pub, meet at a place of worship, meet in a neighbourhood.

"The truth is, on the internet, everything is simplified. When you meet people face to face, it turns out they're complicated."

Prince Harry reinforces that message. "By liking something and sharing something, isn't making change. If you really want to make change, you need to look up from your phones and get out in your communities. On the social media front, educate or regulate."

Toward the end of the interview Prince Harry did some rapid-fire questions which was quite fun.

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Some highlights:

PRINCE HARRY: Suitsor The Good Wife?

OBAMA: Suits, obviously.

PRINCE HARRY: Rachel or Monica?

OBAMA: Rachel.

PRINCE HARRY: Harry or William?

OBAMA: William, right now.

PRINCE HARRY: The Queen or the Queen?

OBAMA: The Queen!

You can listen to the whole interview here, or download it as a podcast.

UPDATE: Dec. 27, 2017, 2:07 p.m. GMT Added quotes.