His three boys – 16-year-old twins and their brother, aged 13 – are older than my sons (nine and six) by a good margin and he spoke with a certain sadness about how he'd 'lost them' – especially the oldest two.
"We used to have such fun together," he explained.
"But now they treat me as if I'm an embarrassment – even when I'm not dancing in front of their girlfriends, or telling jokes to their friends, or cheering them on at football! I used to be their hero."
Then he looked at me with such poignancy that I could swear he had a tear in his eye.
"You've got all this to come, you know. Enjoy your lads while you can. It doesn't last."
His words were still chiming during half-term last week. I spent pretty much every waking minute with my lads, sometimes just with them; sometimes with them and their mates.
At times it was quite tedious, for example, sitting on a bench in an adventure playground while they whooped and cheered as they zipped by on a zip-wire.
But most of the time, it was tremendous fun: kicking a ball about, building a LEGO fort, watching movies, playing board games, taking the mickey, and even making pizzas for when their mum got home from work and their older sister (my stepdaughter) returned from her dad's (who is her hero).
Far and away the best times, though, were the spontaneous cuddles. The youngest would climb onto my lap, grab my head in a lock and whisper: "I love you so much I want to crush your head to pieces!" (Yes, he's an odd boy).
But his big brother was more articulate. As I tucked him into bed each night, he'd kiss me and say: "You're the coolest dad in the world."
And I'd reply, fishing for another compliment: "How do you know? You've only got one dad."
To which he'd reply: "Because my friends say you are, too. And funny."
Which I guess translates as: "You're my hero, Dad."
Now I appreciate that this might come across as a gushing blow of my own trumpet but – hey! – so what? I'm chuffed to bits – especially because I know it's not going to last.
When my boys start sprouting hairs and dropping pitch, they will morph into surly, self-conscious, knuckle-dragging teenagers like my friend's sons.
Their dad is no longer their hero – but an embarrassment. So I plan to revel in my Superdad status for as long as I can.
I'm not unusual. According to a new survey, 90 per cent of children describe their dad as their hero.
Much of the media paints us as cringe-making muppets, when in fact our children are very, very proud of us, giving us credit for a lot of stuff that we might think goes overlooked.
A quarter love us for how we look after our families and fifth appreciate how hard we work to give our families a good life.
The survey, for LEGO, says our kids give us credit for driving, mending and fixing, and helping them with their homework.
But most of all, they think we're cool enough to want to hang out with us and play.
OK, this hero worship might fade during the teen years, but I had some news for my friend.
"What do you think of your own dad now?" I asked him.
He replied: "He's amazing. The way he's dealt with everything since our mum died. The way he picked himself up. He's a great guy. What about yours?"
"Same," I said. "He's the coolest man I know. I just wish I could see more of him because when I do it's like being with a best mate."
That's us dads: once a hero, always a hero, with just a blip along the way.
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