Mr. Duffy goes Bunburying : A Royal Mystery

From the Royal Archives, a hitherto unknown episode in the life of Prince Alfred, youngest son of King George V.
It's February 1934. Daniel Farraday is quite happy being the only Naval Provost at the Royal Navy's outpost in Auckland, New Zealand. But his cushy life suddenly goes sideways. The Hon. Alfred Duffy, a young, rather dopey toff from England, arrives in the city. Oddly, the Navy (and everyone else) can't seem to do enough for him.
Farraday is forced to chauffeur Duffy to Ladymount Abbey: a big country house, inhabited by the highly eccentric Covey-Crump family. It's all uncannily like "Brideshead Revisited" - which hasn't even been published yet!
Somewhat unexpectedly, they're joined by the ravishing Frau Hildegarde von Morkenstein, who's crime reporter for the "Church Times" of London.
Soon after their arrival, there's a murder: and Duffy determines to solve the crime.
The bodies start piling up; there's talk of a ghostly nun; and Farraday begins to suspect that everything's not as it seems...