The Ampersand Papers — Michael Innes

While Appleby is strolling along a Cornish beach, he narrowly escapes being struck by a body falling down a cliff. The body is that of Dr Sutch, an archivist, and he has fallen from the North Tower of Treskinnick Castle, home of Lord Ampersand. Two possible motivations present themselves to Appleby - the Ampersand gold, treasure from an Armada galleon; and the Ampersand papers, valuable family documents that have associations with Wordsworth and Shelley.