Any #brompton experts here?

I was folding my (P line) Brompton the other day and heard a small "ping" sound. Then I saw this small, black, anodized, Phillips-head screw on the ground - but I can't find where it fell off from!

Anyone have any ideas?

The bike still works fine, at the moment: it gets me around the streets of Pisa quickly and comfortably, easily on the train even when crowded, even up&down the 4km long, 350m high hill near my house -- a reliable companion!

@poritzj for holding the rubber seatpost bung in place?

@tlohde @poritzj Rubber insert on seatpost is a hex-screw on older Bromptons, on newer Bromptons there is no screw any more.

Lost the new pung recently (which is significantly lighter than the old one) and put the old one on again, hence I know. 🥴