Turns out Davies and his colleagues were less proud than they were defensive about these knobs. Employing tampers outside their shop at 23-25 Leather Lane in London (EC1) indicated they’d been removed from their intended use. To some this might have violated an ethos of the trade.

Prufrock barista David Robson noted a practical benefit: Davies was always instructing novices to hold the tamper like a door knob. The tampers on the front doors would serve as an early reminder for students attending the barista training school soon to open in the spacious coffee shop’s basement. So clever, I thought: In their spare time the trainees could practice their tamping skills by opening and closing the front doors for customers.

Prufrock co-director Jeremy Challender maintained that the tampers were the wrong size for their espresso machines. Redeploying them as knobs amounted to recycling. Davies essentially said the same thing, only in the wordier fashion that is amongst his personal gifts.

They [the tampers] have been following me around for a few years since a lady customer closed her coffee business down when she moved back to the states. You can see from the right-hand side one it says 55mm on it. Our machines use 58mm baskets. I kept trying to give them away to home espresso users but they kept returning them as they were not the right size…

Okay, Gwilym, you’re forgiven.

Personally I have no objection to their using tampers as doorknobs. It’s good design as well as a groovy decorative touch for a coffee shop or even the home of a coffee enthusiast. Thinking I myself might appropriate the idea for a new closet we were installing in our London flat I browsed Prufrock’s shelf display of knobby tampers.

I liked the black-handled one (extreme right) best but was informed it was not for sale to anyone, anywhere. Not even if I promised to use it as a tamper and never as a knob? No. Not now. Not ever. This sounded unreasonable to me, until I had a closer look at the black doorknob, er, tamper I fancied: