My son becomes the alpha male... and I've a new role
He's holding court in the restaurant. Surrounded by his family, three generations gathered to celebrate the landmark. All eyes are turned to him, his granddad and nan laughing at his jokes. His mother playing her usual gentle cheerleading role.
His views are typically forthright for his age, unvarnished by the dreary stuff of disappointed experience.
His intelligence and thirst for learning enthuses his audience.
To his side I sit and wonder. What I actually feel is a sense of pride, but also displacement. He's doing my job.
I'm on the outside now looking in, a disconcerting place to be after the last two decades of star billing.
My elder son is 21 and we are in London with his grandparents and his brother to mark the occasion.
We are now at dinner in a West End restaurant that's going to cost me too much.
As he expounds another theory, I take myself outside the group and look in.
There's my own father, the passing of time having got him long used to playing a supporting role in these events, all nods and questions, and there's me, white knuckles wrapped around the baton, not sure I want to pass it on.
As I look at my son, more than six foot with indie rocker long hair and Camden vintage clothes, the question arises: what happened to the years?
I can still see his big, round baby head crying out because he's the last in the nursery to be able to walk.
I see him with braces on his teeth, self-consciously trying on his big school uniform, off with backpack to his first music festival and then dropping him off in London only two years ago to begin university life, anxious and half-wanting to return to the comfort of his room at home.
Not anymore. And I see the dinners and lunches and car rides down through the ages, with me holding forth.
I can't hear what I'm saying, but it must be good because he and his brother are listening.
I'm probably mangling life-stories with stuff about film and music and what's right and what's wrong.
And, of course, I'm having to make them laugh. It's in the job description.
And it's all uncontested, because I'm dad. It's what you do. Not anymore.
They've heard it all now and have dismantled much of it, keeping but small bits.
They'll hold on to the Velvets records and the Withnail and I DVD, maybe even retain some affection for terrible football teams (in our case Gillingham FC), but much else can be jettisoned.
And my son is in his element. Earlier in the day, he whirls us around his London, grandparents struggling to keep up, as he points out hidden gems of the city's narrative and regales us with vignettes of student life.
I lived in London 25 years ago, but my city was all black and white, crime and punchy pubs. His is much more exciting, so many more music venues, exhibitions and parties, although there are some stories sensibly to be kept away from grandparents and even parents still wishing they were students.
I suppose all fathers, who exist in what the sociologists would say was the alpha male mode, come to this moment of realisation.
I just didn't expect it to hit me quite so hard over the pasta on Saturday night as I tried to get in a word edgeways. Sure, I've been used to the recent ribbing over clothes (time to ditch the Echo and the Bunnymen overcoat, dad!) and receding hairline.
But now I have to get used to a new role. It's called listening to, and maybe even learning from, my sons.
It's going to be bloody hard, but I'm prepared to give it a go.