Autumn has passed and my friend is forlorn. His son's room is empty and sometimes he wanders in, opens his child's cupboard, picks up a book, rearranges his drawer. In everything, there is memory. No tragedy has taken place but a gentle sadness has visited my friend. His son has left home, gone to university in another land, unfurled some wings, changed his address. He does not need his father's hand any longer to cross roads or even seas.

When a child leaves home to study, work, marry, it is a joyous moment - no more parent-teacher meetings to attend or clean-your-room lectures to give - and an affecting one. When a child returns, he will be someone else and wearing a tattoo you did not authorise. He may not stay but only visit. It's like a small boat has slipped its moorings and it is a necessary adventure and yet, for parents, an awkward one. Loss, we discover, has many forms and separation has many contours.

When my daughter wanted to leave home years ago to live on her own in Melbourne - just a 20-minute walk away - I was in agreement and yet miserably grumpy. We don't appreciate presence till it is gone.

I will call her every day, I exclaimed. "No, you can't," said the wife. I will casually stroll over and say hello, I ventured. "No, you won't," I was instructed. A child finding herself, I understood after suitable melodrama, was also about a parent letting go. Within hours of its birth a wildebeest calf is on the move, for survival on the savannah demands speed. Humans, too, must let their children run.

My friend, who has clearly dealt with corporates too long, calls this a "demerger", a cold-blooded term for a time of apprehension and yet also curiosity. What will become of our children? Have we armed them well enough? Do they know anything?

Will they remember to change their sheets and not get into cars with drunk drivers? Did we teach them sufficiently about tidiness, flossing, strangers, sex, changing bulbs, compassion, ambition? Will they remember or will our voices be drowned out by new, exciting ones urging them to have one more Jagerbomb?

And so, confronted by all this, my friend's response was to give his son something unusual before he left. Something he could carry, keep, frame, file, look at, pass on. Something powerful built of paper.

Letters.

My friend used to be a fine journalist so he understands words, appreciates them, knows their weight. So every day during his son's last week at home in August, he wrote him a letter on Xerox A4 paper and left it by his son's bedside so it would be the first thing he saw in the morning.

So much we want to say to people yet we are diverted by the incidental - the movie we saw, the sofa we bought and Trump's latest trespass. In the midst of cosmetic conversation, the meaningful gets postponed. But letters, in some ways, are uninterrupted monologues of more considered thought. Longhand remains a prudent art in a Twitter world.

These letters were not especially cautionary in tone or instructive - there was no enlightening advice on how to iron cuffs and collars - though an essential part of the parental gene is to offer advice. We prefer to call it suggestions. So my friend urged his son to invest in people through acts of kindness and empathy, to think like a statesman, to ask people for advice. And to date.

But the letters primarily had another purpose. You could call them early pages from a family's memoir. Our greatest inheritance sometimes is the knowledge we carry with us and this is what my friend wrote down for his son. Knowledge about his family, about his grandparents, about who these people were and where they came from and, thus, who he is. He was offering his son something profound. A sense of belonging.

However self-made a person might be, part of who we are - even the way we look and behave - is always connected to someone else. We are not just anybody, a statistic on a foreign street, because we come from somebody. We hail from particular tribes and their stories become our anchors. But someone has to tell these stories.

This is what my friend does - he educates his son. He sketches profiles of the boy's grandfather and grandmother and hands them over, he erects through words a scaffolding of the past.

He tells the boy of his grandfather's cricket skills, his financial struggles, his wit and calligraphy, his spirituality and short-temperedness. He tells him how his grandfather walked from shop to shop selling ball bearings and every day recited the azaan with the "sweetest" of voices.

He tells the boy of his grandmother's kindness and her resolve, for her studies were discontinued as a child yet she educated herself by reading the newspaper every day. He tells him how she was an amazing storyteller and had reservations about his marriage - my friend, a Muslim, is married to a Hindu - and yet after a two-week silence never brought it up again.

He writes these mini-biographies down plainly and honestly, painting clear-eyed portraits that avoid exaggeration and the maudlin. They are, I think, acts of duty, of fear and of love.

Perhaps my friend believes that handing over the past to the future is his responsibility as an elder. Perhaps he is also scared that his son might not come back, that he will wander off into the world, disconnected from land and family, not rooted to anything. Now he can always pull these letters from his pocket and know he is a thread in a larger tapestry.

The letters are also a message, a father telling his son that he understands, that he knows the young man must leave, it is time, he must travel and learn and must do it alone. The letters are an acceptance of this parting, that there are no beginnings without ends.

Maybe the son understands, too, that the letters are a gift from a parent who is hurting. And so, even though the young man is not demonstrative, on the day he gets the first letter he comes home in the evening and stands by his father's side and quietly holds his hand.

What did you do, I asked my friend.

"I wept," he said.