Greenvile Collins (1643-94) is the most important Royal Navy officer you have never heard of. But he was well known to Samuel Pepys, and worked personally for Charles II, James II and William III as hydrographer, navigation instructor and royal yacht captain. The charts by themselves would ensure his place in history, but Collins also made history through his actions. As navigator of the King's flagship during the 'Glorious Revolution' he perpetrated an ingenious deception, granting the Dutch army crucial extra time to mount their invasion. This has never been written about, perhaps because historians tend not to be navigators, yet it's all there, in Collins' 1688 journal, hiding in plain sight. This new study both explores for the first time Collins' charts as navigation aids, as well as how he changed the course of history.