The Mermaid and Mrs Hancock by Imogen Hermes Gowar

Before Imogen Hermes Gowar was a writer, she worked at visitor services for the British Museum. There she came across a rare and hideous artefact, a mummified monkey stitched to the tail of a fish. Fascinated, she plunged into the story that became her first novel, The Mermaid and Mrs Hancock. Thanks to a feckless captain, Jonah Hancock -- a merchant -- loses a ship but finds himself apparently in possession of a mermaid. Gowar wickedly evokes the brothels and coffee shops of Georgian London, abuzz with talk of this extraordinary creature.