Hi Sandra,
How interesting. Margaret Cubbon's will might have attachments which refer to the forged document or even have a copy of the doc. itself, seeing that it referred to her will. If so, they would have further additions saying that it was a forgery, etc. No doubt you will be sending the transcript to Brian for his website?
I have seen attachments which are dated various dates up to 20 years after the original will, so it might have Robert's one there as well, or just an Inventory of his assets.
Sue