Note the crack in the frame right in the centre of the picture. The design was improved on later Bromptons. The holes for the hinge machine screws are also worn. This happens if the hinge screws wind their way out with folding and unfolding, and whilst that's not good, in this case the wear is not extreme so only the cracked frame makes the bike unusable. Birmingham Bike Foundry told me that whilst they could weld the frame, they also told me that in their experience the weld would likely soon fail. I also consulted with Red Kite, who consulted with Brompton. Apparently the only triangle of this type they have is the one attached to a bike they have in their museum. Red Kite also spotted that one of the frame hinge clamps had cracked (thank you), but they are easily replaced and I have done that.
