My attempt to quit Diet Coke does not start well. I finish my stockpile on New Year’s Eve, suckling from a two-litre bottle like a baby drinking from the teat.

On New Year’s Day, I wake up hungover and watch TV in bed with my boyfriend. We order pizza. “Add a can of Diet Coke,” I instruct him. “I thought you were quitting?” he replies. My head is pounding; only the caramel smack of Diet Coke will do. “Order it,” I say, my tone leaving no room for discussion. When it arrives, I down it, making little whimpering noises of pleasure.

The following day is worse. I find myself craving Diet Coke in a way that is alarming and unexpected. I envisage a tiny part of my brain – roughly parallel with my tongue and upper palate – that won’t become activated unless I drink Diet Coke. I want to dump a bucket of Diet Coke on this spot and watch it fizz. I know that my headache won’t go away otherwise. I feel horrific.