Hi John, many thanks for your very interesting response. I had never heard of the book you mentioned and a quick search has failed to find any more copies but it sounds fascinating.
Who was the author, presumably s/he was the great nephew of Charles Coleman Laing in the quote you mention ?
The other people mentioned don't ring any bells at the moment apart from Arthur David Cunyngham who was one of the executors of his will. He died only 4 years after publication aged 46. His wife Mary Ann Helen, née Gordon, died in 1919.