I am just INCREDULOUS that you thought this would be OK. I’m not kicking you out, it’s fine. I just… can’t believe that a person could do this!” She stood in front of me with the expression of a person who’s dug two graves before embarking on a journey of revenge that’s ending here, now.

It was the first hot morning: that thick, curried air, all the commuters carrying their jackets and stopping on walls to apply plasters to their sandalled heels. I’d found myself with a free half-hour between dropping my daughter at the childminder and starting work, and felt a little drunk at the prospect of time. I bought a croissant from the bakery, almond, and sauntered on feeling decadent and European. Ahead was a café, with tables on the pavement, empty but for a customer coaching the waitress in the art of making his takeaway latte creamy, “but not dense”. “You’ll learn!” he said, chuckling as he swung his ponytail like the most popular girl at trampolining.

When he left, I ordered a coffee, and asked the waitress if it would be possible for me to eat my bakery-bought croissant at one of the tables in the sun. She brought the coffee over a minute later, with a plate, and napkin, and I basked again in the unlikely joy of nowhere to be. As I took a bite of my croissant, almond, the woman approached. Small, blow-dried, she quivered with a kind of pre-rage, a rage that marched ahead of her on kitten heels.

“I just wanted to say,” she shouted, “that I’m the manager here, and I can’t believe that you brought your own food into a food establishment.” I offered a sort of strangled apology, an insistence that the waitress had said it would be OK, and we both stared at the croissant with varying degrees of accusation. A familiar heat settled on my skin, the realisation that I am terrible and have yet to learn the rules of a life. What was I thinking? There I sat, a meat piñata of shame and shock. It was confirmation, at last, that I was made of something less than flesh and conscience, something akin to papier-mâché left outside in a storm. “I’m incredulous. I’m just INCREDULOUS that you thought this would be OK.” I started to stand, gathering my assembled bags. “I’m not kicking you out, it’s FINE. I just can’t believe that a person could do this.” “It’s obviously NOT fine, so… I’ll go,” I said, feeling a little better actually. Because something was actually happening. Somebody was properly shouting at me. Not just typing, or rolling their eyes. She was shouting at me, and it was daylight and nobody was high or ill or startled from being reversed into by a slowly parking car. It was just us, in an empty café and something was happening.

“No. Sit down. Drink your coffee.” She looked as if she was going to either cry or sneeze, that unstill crackle of neon, and so I sat, and she began again. “I’m just saying, I’m incredulous. Speechless. What kind of person brings a meal into a café? Thinks that’s fine? Asks for cutlery?” I hadn’t asked for cutlery. The coffee had arrived in one of those handled vases from Ikea, a litre or so of boiled anxiety. I started to down it. Honestly, I was pouring this stuff into my head so fast I felt like I was drowning, but on I poured, a contestant on a Japanese game-show, a sweating vessel.

I was looking her in the eye, and I was drinking her coffee, and I was eating my food on her premises. She obviously went to the gym. She had those arms where you could see all her workings, all the tiny muscles taut like spaghetti and meatballs. I wondered if she was going to hit me, and if so, whether this was the kind of occasion where she’d be aiming for the face.

Did she… did she want me to eat the croissant in front of her? I tentatively took a bite. She nodded, her suspicions confirmed: it was food, and I had been planning to eat it. She walked back to the counter, where she stood in the shade, fuming. So I ate my croissant, and looked out at the street, charity shop obese with donations, the Poundland, Costa, dentist, Clarks.

At the till, I dropped a generous tip into the jar with what I felt was great drama, and as she handed over my change, she looked away slightly. “I’m sorry if I was a bit sharp,” she said, sharply. “I think it’s because I’d just been reading about Manchester.” Which I hadn’t been expecting at all.

Email Eva at e.wiseman@observer.co.uk or follow her on Twitter @EvaWiseman