I was having lunch with two friends I first met at nursery school. Friendships spanning four decades can be very deluxe. When people know almost everything about you, have visited you in all the places you have lived, from the L-shaped room in Kilburn without heating or hot water to the mews flat in the West End with “second housemaid” embroidered on the eiderdown; when they know all your victories and the disasters, it makes for a lovely kind of confidence. Even the passing of the soya sauce means more.

These friends both know I fought a little too strenuously for the part of Miss Piggy in the second year juniors. They might tactfully say it was my forceful campaign that showed our teacher I was the right girl for the job. They know the tiny boy who played Kermit covered himself in green make-up manfully, frogfully, before each performance, and tried to keep his head in the face of my pink feather boa.

In turn I remember the words of their best junior poems: “Black is the colour of my wellington boot/Black is the colour of the night owl’s hoot”; their prowess on the rounders pitch and the violin; and the utter delight one felt when her thumb got shut in a train door and she was finally allowed to give up the instrument.

One had five or six siblings with extravagant names and more extravagant nicknames, so I thought she had 10 or 12 at home. One had a noble father who encouraged all his secretaries to go on courses so they could become managers and fulfil their potential. Once, at her house, he suddenly asked me, “So, if area is measured in squares, what is volume measured in?”

“Triangles?” I offered.

We all remember the boy in our class who became hysterical with grief when he only got nine out of 10 in a spelling test. Of course, we rarely talk of the past but it is there in front of us, hovering over the table. I sometimes think it makes the food taste more piquant.In the afternoon I went to visit another old friend: Selfridges. There was a time nearly 20 years ago when I went there every day. I rarely bought anything, I just popped in like some mild-mannered janitor, to check the stock.

If I ran a department store, I would staff it with people who care deeply about the meaning of things, who like to muse about what fuels the drive to purchase: be it reward, revenge or repair. Selfridges used to fall down in this regard, its assistants were too crisp and, well, normal, I suppose. This seems to have changed.

On the second floor, looking for a present for a friend in ladies’ fashion, I encountered a salesman who was no stranger to such rules of engagement. Sometimes you want to buy something and make a fast getaway. This was not one of those times. I wanted something for a friend — a dress, perhaps, in return for the million and one kind things she has done for me. “It is a complicated thing to buy a dress for another woman,” the assistant told me. “It can backfire.”

“Can it?”

“Of course, it’s not just that the chances of it fitting perfectly are quite small but it is so personal, a dress, it could feel as though you are trying to control her, take over the reins of the friendship. Is she younger than you?”

“Older.”

“No, no, no,” he said. “No good at all.”

I loved the idea that our friendship had reins. Was it a horse that she and I rode on together? Were we sitting in the carriage, fighting for the steering? And why had our friendship been located in pre-motorised times? Did he take us for bonnet-wearers? (We’re not, are we?) We peered together at the dress I had chosen. It had a bodice of thick black satin and a skirt of lustrous wool felt. It was what a Henry James heroine in mourning might wear on her first night back into society.

“It is a very heavy thing to give someone a black dress,” he said. “It’s too assertive. You want something lighter, slightly frivolous, that doesn’t say these serious things.” He brought me an ivory silk shirt with pink stripes and little pink discs, a print that might have been considered quite space-age in the 1930s.

“Something like this. It’s like a box of sweets, it’s light, it’s like a smile. It’s fashiony, no?” He was right.

I bought it and felt the rays of his approval warming my hands and nose. It was all I could do not to ask him about the many other dilemmas that torment me in life, but I held myself back.

I might just return tomorrow.

— Financial Times