So what do I think, now I've done the dastardly deed?
Well, to be honest, I thought that the outer cover was of better quality than I would have imagined - strong, durable and pliable, perhaps more so than usual because I had "fed" the leather some time ago.
But, and it is a big "but" for me; I now realise that my attempts to "train" my filofax in the dark art of flatability were in vain. Although I can only comment on the construction of just this one filo, there are simply too many layers of stiffening material underneath the outer layer of leather.
But that has to be only my opinion.
My Filofax Finsbury is no more, but some of the parts will live on in other incarnations. The ring mechanism is destined to be used in a bespoke custom leather binder project, and the original Finsbury leather cover just happens to be the right size to patch a hole in my bicycle panniers.