Who Was John Harrison?

John Harrison (1693-1776) was an English clockmaker who was the first to solve the problem of how to claculate longitude at sea.  During the 17th Century trans-oceanic voyagers had experienced great difficulty in being able to plot where a newly discovered land actually was, so that it could be drawn on a map or found again in the future.
Also, knowing exactly how far east or west you were of any given point (usually London) was vital in plotting your route, or you could end up missing your intended destination.
John Harrison was the first to develop a prize winning design for a chronometer (maritime clock) which could keep an extremely accurate track of longitude, over a very long sea journey.
He submitted his design in 1714 in a competition set by the British Government.  He was eventually recognised as the winner with his H4 design in 1772 !