Last week we visited the National Trust property in Hinton Ampner and saw all sorts of decorations and ornaments made from a purplish stone that looked a little like spotty marble. I asked the steward what it was called and he very kindly gave me a very detailed answer. The stone is porphyry which comes from just one single mountain in Egypt, and it was very popular in Regency England for interior decoration. The name is also linked to the medical condition porphyria which turns the urine of sufferers a reddish purple. George III is thought to have suffered from this condition and it would also have been responsible for his episodes of 'madness'. Stay with me, I am getting to the point. So, when I got home that evening I started this book, and by coincidence it was related to the inherited condition of porphyry and how it came into our royal family via the German House of Hanover. Set in the mid 18th century, it is also the time of the portrait artist Thoma...