Sweet Danger written by Margery Allingham performed by Francis Matthews on Cassette (Unabridged)

Way back during the Crusades, Richard I presented the Huntingforest family with the tiny Balkan state of Averna but since then the kingdom has been forgotten, until circumstances in Europe suddenly render it extremely strategically important to the British government.

They hire unconventional detective Albert Campion to recover the long-missing proofs of ownership - the deeds, a crown, and a receipt - which are apparently hidden in the village of Pontisbright. On arriving in Pontisbright, Campion and his friends meet the eccentric, young, flame-haired Amanda Fitton and her family who claim to be the rightful heirs to Averna and join in the hunt. Unfortunately, criminal financier Brett Savanake is also interested in finding the evidence for his own ends.