Send a message to the person who requested a photo of the grave monument of James Watson with the following comment:
Hi there, I am interested in this photo because I have been asked to photograph the gravestone for a book. If possible, I would like to see the higher quality version you have to give me an idea what to expect or instead to make an offer of payment to you or copyright holder instead of going up to Edinburgh myself (if book editor agreeable and if that would be ok with you/copyright holder).