"This fragment of volcanic rock was brought to England from Pompeii by Sir Hector Thorogood on the occasion of his visit to Italy in 1862." So runs the legend on a label attached to a lump of stone found in the cupboard under the stairs of a Hampstead house.

The stone yields a casket containing two manuscripts covered with a strange script, part Greek, part Hebrew. Months of patient archaeological detection reveals that it was written in the first century A.D., by Nathan, the son of a prosperous landowner in Jericho, subsequently sold into slavery, and later the confidant of kings and queens. Inextricably bound up with his story is the fate of Berenice, daughter of Agrippa I, King of Judaea, and one of the most controversial figures of the period.

How reliable was this account? Was the document a complete forgery? If not, how far was Nathan guilty of distortion? These and other questions are posed by Paul Capon, who tackles this unusual subject-matter with skill and perception. The result is a novel of great originality.