10am, Monday morning. My editor asks me to attempt to drink 25 cups of coffee by 1pm and write about what that is like. It’s OK, I won’t die, he – and science – says.

Coffee has been previously thought to stiffen arteries and increase the risk of a heart attack or stroke, but a new study by researchers at Queen Mary University of London and part-funded by the British Heart Foundation has found that drinking five cups a day – even 25 – is no worse than one.

I’ve had one at home, quite strong, from the moka pot, with a dollop of frothy milk, and normally I’d have one or two more over a morning. But this is research, I take my journalism very seriously. I have two more quickly, black, from the office coffee machine (Colombian beans, quite nice, in moderation). And then another, even though I really don’t want it.

11am. My arteries might not be hardening, and my heart doesn’t seem to be racing, but – and it’s a big but – I’m feeling a bit queasy and not at all like more coffee right now. And I’ve had only four. Just 21 to go, then. Except that’s the quota for the day, and I have just got the morning, so maybe I can get away with 12? Still, the idea of another black coffee makes me feel ill. I’m going out for one.

12pm. I go to Pret a Manger for a cappuccino. Extra shot? That would count as two right? Shot me up. And a receipt – I’m totally expensing this. But that’s still only six. I suppose decaf would be cheating …

1pm. I manage two more. OK, one and a half, seven and a half in total. That’s it, I’m done. I’m not just feeling nauseous, but jittery and shaky, too. Who the hell are these caffeine freaks who drink 25 coffees a day?

I don’t care if the pointy-heads at Queen Mary say it’s not doing my heart health any harm, I feel grim. Also, coffee breath! Perhaps they should do a study into that: the effects of 25 cups of coffee on your oral hygiene. Now I’m going to see my editor, to snap at him, and breathe on him.