I’m not sure quite how we ended up with multiple sets of these tongs, especially as the pin that holds them together appears to be made of cheese and eventually fails to manage the one simple job that requires its presence.
Fortunately I managed to find a screw of the right size to replace it in the workshop (which has still not entirely recovered from flooding almost a year ago) and with a pair of nuts on the other end to lock everything together, one pair will hopefully provide years more service.
With a second failed pair, I tried to be slightly more clever and used a brass screw, giving the tip of the screw a decent “tap” with a centre punch after putting on a single nut, the idea being to distort the thread and prevent the nut from coming off. It looks neater, but only time will tell if it works.