While modern excavation and radiocarbon dating has undoubtedly advanced our knowledge of the sequence and date of the monuments, their purpose and meaning is still hotly debated. Indeed no previous century has changed its mind so often as the twentieth - or provided such a welter of differing opinions. Each theory has as much to say about its own time as it has about prehistory. The stones have been used to enhance the authority of the Bible, to endorse the civilizing mission of the British Empire - and to argue that the Ancient Britons could work a computer. In a reaction to modern industrial society, they have been credited with spiritual powers and natural energies.

Even the views of modern archaeologists often seem to reflect the latest academic fad, rather than a lasting solution. Riddles in Stone is an entertaining and instructive account of a debate on a subject of endless fascination.

Federico García Lorca was born in 1898, in Andalusia, Spain. A poet and dramatist, and also a gifted painter and pianist, his early popular ballads earned him the title of 'poet of the gypsies'. In 1930 he turned his attention to theatre, visiting remote villages and playing classic and new works for peasant audiences. In 1936, shortly after the outbreak of Civil War, he was murdered by Nationalist partisans. His body was never found.