How an eighteenth-century hoax has taken in Dava Sobel and other historians

Most people know something of the events in 1714 when the British government instituted a prize for the discovery of a successful way to find longitude at sea. The aim was to reduce the heavy toll of shipwrecks caused by the crude navigational method of dead reckoning. Dava Sobel gave new life to this episode in her bestselling book, Longitude: The true story of a lone genius who solved the greatest scientific problem of his time (1995), which inspired the widely viewed television programme Lost at Sea (aired in 1998). After these came a feature film directed by Charles Sturridge in 1999, starring Michael Gambon and Jeremy Irons. All these versions place at their centre the heroic figure of John Harrison and his struggles to perfect a clock which would finally carry off the prize of £20,000. Meanwhile, an early rival who figures in the tale has gone down in history as another projector from Yorkshire, named Jeremy Thacker. Unfortunately Thacker never existed and his proposal now emerges as a hoax.