The history of the Royal Observatory, Greenwich has been revised to coincide with the Millenium. Color illustrations and updated text tell the story of Greenwich from its foundations in 1676 to its present status as Longitude 0, the world's Prime Meridian for measuring longitude and time. The book covers the importance of longitude for navigation and traces the history of Greenwich Time, the basis of universal time-keeping.

The book is co-published with the National Maritime Museum, where Derek Howse was the former Head of Navigation and Astronomy.