I had my own set of keys to Gillie’s house. I will, as I said at her funeral on Thursday, give them back to her daughter Jules. But holding them these past few weeks, I have been thinking about what a key actually means between friends.

It’s not about access. Rather it’s about the decision that was made – at some point, probably without ceremony, and certainly without being made a fuss of – that you are the kind of person who should be able to let yourself in. That you are, to use a word that doesn’t quite capture it, trusted.

Gillie’s friendship worked like that. Unconditional in practice, though not in the sentimental sense. She had standards. She had views. She was, quietly, firmly, a second-wave feminist who had given her daughters a train set and stacked Spare Rib on the shelves when I was young enough to find it illuminating. She was a Samaritan. She became a psychotherapist. Into her eighties she was volunteering at the food bank.

She never just drifted through life.

She was also, technically, my ex-sister-in-law. A category that the English language has never been able to make sound warm. The marriage to my brother ended. That’s the official record. What the official record doesn’t show is that by the time the marriage ended, Gillie and I had been in each other’s lives for the better part of thirty years. You don’t simply reclassify that.

At her wake I talked with Stephen, her first cousin, who had also spoken. We recalled the old saying: you don’t choose your relatives but you can choose your friends. He was thinking about his own journey with her, from obligatory family connection to something chosen.

I was thinking about mine.

The thing about friendship with someone like Gillie is that it doesn’t require maintenance in the way that some relationships do. You didn’t have to perform it. You could arrive, with or without warning. I had the keys – and within minutes you would be talking about the things that mattered: the friends she had lost, the books she was reading, the next holiday, the grandchildren coming to stay, whatever was coming next. There was always something coming next.

She is gone now. The gap where her friendship was is very raw.

I shall give Jules back the keys. But perhaps not quite yet.