Catherine & Davida time capsule, kept open

I have known you both for the entirety of my life and for ten years longer than that. You are the people I learnt patience from, and impatience, and how to argue across a kitchen table without anybody actually leaving. If I have any idea what a good marriage looks like, it is because I have been quietly cataloguing yours since I was tall enough to see over the worktop. Happy thirty. I love you the same as ever, which is to say, completely.

For C., — The book is closed, for now. I have written this on the morning of, as I have written most things in the last thirty years: at the kitchen table, with the radio on low, while you finish in the other room. The flat above the butcher's, the green carpet, both children, the renovation that did not end, Kyoto in the rain, all of it — and somehow still the best part is hearing you come down the stairs. Same time next year. — D.

The Glasgow flat. The terrible green carpet. The radio always on low. You fed me dinner once a week through my PhD and pretended not to notice the wine going down. You taught me what a household sounds like — two people in different rooms, perfectly content. I have been trying to replicate the recipe ever since, and I am closer than I was.

I sat between the two of you on a coach to Stirling in 1994 and decided, within forty minutes, that you should probably get on with it. I am happy to confirm, thirty years later, that I was correct, and that I expect royalties — payable in the usual currency of Sunday lunches and the occasional letter.

I stood beside you in St Cuthbert's wearing a dress I have never forgiven our mother for choosing. What I remember most is David's face when the doors opened — entirely unsuitable for a religious building. Thirty years on, he still looks at her like that. Insufferable. Wonderful. The dress, I have burned.

Mum, Dad — I am told a wish is required. Mine is selfish. Please keep doing Sunday lunch indefinitely. It is the only fixed point I have and I would like another thirty years of it. Love, your second-favourite child.

You took me in for a month after Stephen left and never once made me feel like a guest. I drank all your good gin. I have not forgotten. I owe you a bottle and an anniversary, in that order, and I plan to deliver both in person before the summer is out.

You stayed with us in Kyoto for two weeks and left the kitchen cleaner than you found it, which is, we are told, the highest form of British affection. The garden still remembers you — we kept the maple where you said it should go. So do we. Onward, dear friends, to the next decade.

My brother is a difficult man. You have made him a less difficult one. This is, on the available evidence, a Nobel-level act of patience. We are all in your debt. Thirty years, Cath. Thirty more, if you can stomach it.

Ninety-five years old and I have outlived most things, but not the pleasure of watching my daughter marry well. You have been good to her, David. You have been steady when steady was not fashionable. Continue. With all my love — Mother.

You let me practise the eulogy for my own father in your living room, twice, without flinching. That is the kind of friendship most people only read about. Thirty years for the two of you, forty for us. Onward, and may the road be kinder than it has any right to be.

From the next-door neighbours — thank you for the parcels we have collected, the snow you have shovelled, and the Christmas Eve cocktails that have, against the odds, become a tradition. We will keep showing up at your back door uninvited for as long as you let us. Thirty more, please.