The story of the problem of longitude is well-known, with the British Board of Longitude and John Harrison's marine chronometers playing a major role. The British horological industry produced some of the finest navigational and military timepieces in history, and today that history is exemplified by the large crowds of tourists that visit the Royal Observatory, Greenwich, to take their photo standing over the prime meridian. This coming weekend in London, the British Horological Institute will host a conference on navigational and military watches featuring some of the world's foremost experts in the field, and you don't want to miss it.