Thanks all. OK re the spring, got that... re the barrel - reason I asked - it's not bent, it's perfectly straight - but not inline with the cylinder! It's off to the left, by about 5mm at the front sight - certainly as-is a diopter would be unusable, would run out of adjustment. Perhaps that is why one is not fitted! Also because of this one must really press hard against the cheekpiece to align rearsight to the front.

What could be the possible cause for the barrel being off at an angle? Shoddy Webley workmanship? As above - it is straight, and looks to be nicely fitted into the cylinder forward block.