Legendary interviewer Sir David Frost used to love nothing more than playing football in the back garden with his three sons, Miles, Wilfred and George. But quite often, their games would be interrupted by the sound of ringing inside.

“Mum would come out and say to dad, ‘The President is on the phone,’” recalls his son Wilfred Frost, 39, also a journalist, smiling at the memory today. “And Dad would tell us, ‘OK, boys, I’ll be back in a minute’.”

Still, the unusual distractions never got in the way of David’s first love: his wife Carina and his children. And speaking exclusively to the Express, Wilfred recalls how whatever else was going on in his life, his father always put his family first.

“Dad was always working a lot and travelling a lot, but he was very present for us. He was a fantastic father,” he says. “We were so fortunate in so many of the things we got from our parents – amazing homes or holidays or education. But all of that is trumped massively by the sense of love and support that they gave us.

“Despite Dad caring hugely about his career and working ridiculously hard, we never got any sense that that came first. He was very clear that we came first.”

Wilfred, who is married to Kaley and has a young son Miles, continues: “If we had some of his famous friends round for Sunday lunch and a couple of my friends were there as well, he had just as much time and interest in my friends as the famous people.

“Clearly, people loved his company. I just feel very lucky because the time I spent with Dad was happiness. Mum, my brothers and I had more of that than anybody else. We were very, very fortunate.”

Yet it is Wilfred’s journalistic capacity that has come to the fore this year, as he has produced a fascinating six-part series on Sky Documentaries, David Frost Vs, about his father’s celebrated interviews.

In an astonishing career that encompassed more than 10,000 interviews, David sat down with all of the most iconic figures of the second half of the 20th century.

He extracted extraordinary revelations from presidents, prime ministers, kings, queens and celebrities. He interviewed everyone, from the Beatles and Muhammad Ali to Benjamin Netanyahu and Vladimir Putin.

David was the only person to have interviewed all eight British prime ministers who were in office between 1964 and 2016 and all seven US presidents who served between 1969 and 2009. And the series underscores how enormously influential he was in 20th-century politics and culture. Wilfred says: “Dad had a front row seat as the most important moments of the postwar world unfolded.”

Most famously, in 1977, David persuaded former president Richard Nixon to give his first interview since resigning from the White House three years earlier, as a result of the Watergate scandal.

Over 28 hours of interviews, David landed a world exclusive: he got Nixon to apologise for lying to the American people. The ex-president confessed: “I let my friends down, I let my family down.” The interview spawned an acclaimed play Frost/Nixon, written by Peter Morgan, later turned into Ron Howard’s 2008 film of the same name.

This astounding coup is the subject of the first episode in part two of the series – part one aired in February and March – which recounts some of the most memorable, era-defining interviews conducted by David, who died aged 74 in 2013.

Wilfred, who is speaking from his living room – where a splendid photograph of his father hangs on the wall behind him – is overflowing with fond memories of David.

“He obviously had to work on Saturdays because for most of our childhood, he presented Breakfast with Frost on a Sunday morning. But if we went to drag him away from his desk to play football with us, well, it was never a battle at all,” he laughs.

“Dad was a great sportsman and could have played sport to a serious level. We all loved sport. We were three boys a year-and-a-half apart each. And so, it was always two-on-two. I felt for Mum, as she didn’t massively want to partake in the doubles tennis or the two-on-two football matches.”

David’s enthusiasm on the sports field never waned. “Right up until the end, he was still good,” continues Wilfred, who has followed in his father’s footsteps by becoming a very accomplished presenter on Sky News. “He held his own. On our New Year’s holidays in Anguilla, we had these rather competitive games of football on the beach, and Dad always played.”

You certainly get the impression that it was a very happy household and that David created a positive atmosphere. George remembers: “Dad was always incredibly optimistic. When it was pouring with rain on holiday, the sun was always just about to come out.”

Wilfred, who sadly lost his older brother Miles to hypertrophic cardiomyopathy in 2015, spent his first five years after graduating from Oxford University working in finance. He only switched to television presenting full time in 2014, when he became the co-anchor of Worldwide Exchange on US news channel CNBC.

This meant that he never had the opportunity to take professional advice from his father.

“He died before we got to that point,” sighs Wilfred. “Yet I do think I share some traits with Dad. It’s not surprising that someone who lived around him for 30-odd years might happen to pick up some similar traits.

“The thing that’s sad is I just would love to generally be bouncing ideas off Dad. He might also get a little bit jealous, as I’ve got one or two big interviews coming up!”

Wilfred trained to be a TV journalist for two years without his family’s knowledge. He says that at first, he felt the pressure of following in his father’s esteemed footsteps. “I felt very intimidated initially, which is why I did it so secretly.

“Part of the reason why I didn’t tell anybody was because I thought, ‘I’ve got to see if I believe I can do this before I open myself up to the potential flak.’”

In the event, Wilfred has not received much criticism about nepotism because he is manifestly very good at his job.

“I feel lucky about how things have unfolded. My track record is out there and speaks for itself. This is an industry where you’re doing live TV every day, and you’re going to either sink or swim. I think it’s harder for people to say, ‘Oh, you only got where you are because of your surname.’”

In fact, Wilfred relishes people likening him to his father. “Do I get bored with people mentioning Dad and making comparisons with him? Absolutely not. My face lights up because it reminds me of Dad.

“People in general are so warm, I find. But if I ever do get that snipey ‘he will never be as good as his father’ type of question, which is rare, that even doesn’t bother me because I know I’m not going to be as good as him. In my eyes, he is the greatest of all time. If I can achieve half of what he achieved, that would be insane. So I love any mention of Dad.”

Wilfred even revels in the impersonations of his father that people often do for him. “I always get Rory Bremner to do an impression of Dad when I see him.”

David Frost Vs – which features in addition to his classic encounters with Nixon, some standout interviews with Elton John and all the major players in the Middle East – reminds us why he has been described as “the most talented journalist in British broadcasting”. One of his strengths was his immense likeability. I interviewed him in 1997 and have a very clear memory of an overwhelmingly warm and charismatic man. Wilfred says: “Dad was such a just fun person to spend time with, which I think played a part in why he was so good at what he did.

“People just enjoyed being around him and spending time with him. So whether there was going to be a camera there or not, he had a strong ability to attract the most interesting people.”

David was also fascinated by other people. “The one undeniable thing that I think made him such a brilliant interviewer, which you can’t teach, is a genuine interest in people.

“Dad would love stopping to talk to anyone. It’s like going on a first date – thank God, those days are behind me! When someone’s interested, you sense it, and it just breeds a more free-flowing conversation.”

Elton explains why David’s approachability made him such an outstanding interviewer. “David could draw the best out of you because he was a human being. He was never intimidating. He was a friend. I trusted him. It seemed natural just telling the truth.

“David had a way of getting you to admit things that you probably wouldn’t admit to someone else.”

Former US president Bill Clinton was similarly impressed by David’s peerless skills as an interlocutor. “He got people to talk because he inspired trust. They thought, ‘This guy is going to be straight with me.’ You have to be able to listen to each other, and we desperately need more of that today.”

Wilfred reflects on what motivated him to spend many years on this labour of love. “One aspect driving me to make David Frost Vs was to celebrate Dad’s legacy, to do it justice, and to remind people of how brilliant he really was.”

He found producing the series a very moving experience. “I’m 39, and Dad died 12 years ago. But I still miss him.”

What does Wilfred think his father would have made of David Frost Vs, then? “I think he’d love it. He’d love the fact that everyone’s talking about him again and praising him! If I can deliver that for him, then that’s great.

“I set out on this project with my brother’s backing to try and repay Dad for all that he gave us. And I do feel like I’ve achieved that. I love my day job immensely, and I throw everything at it every single day.”

But Wilfred adds: “I don’t think I’ll ever have, professionally, as rewarding a feeling as completing this project because it’s not for me – it’s for Dad.”

David Frost Vs Part Two starts at 9pm on Sky Documentaries on Wednesday