Thrones & Principalities is the third book in the action-adventure audio serial Valentin & The Widow by Andrew Wheeler.
Lady Rosewood and her valet Sacha Valentin have traveled to Cairo, where a young woman in the Prince of Wales’s retinue may be the key to a dastardly Dominion plot to forever change the British Empire. Deadly acrobats, mad mystics and a ferocious female bodyguard await them at the heart of the ancient kingdom
I feel that this series started well but went downhill after the first book. I'm finding it hard to remember all the details, but there were assassins and ancient Egyptian artifacts, and a child who was the centre of a diplomatic intrigue. It felt something of a mess, and I had to make an effort to finish the book.