More than 2,000 military maps and related items collected by George III have been posted online by the Royal Collection Trust to commemorate the 200th anniversary of his death. As the Guardian reports, the collection “features material from the 16th to 18th centuries, from highly finished presentation maps of sieges, battles and marcheso rough sketches drawn in the field, depictions of uniforms and fortification plans, providing a vivid contemporary account of important theatres of war in Britain, Europe and America.”
George III was apparently an avid map collector. At his death his collection numbered some 55,000 maps: the maritime and topographic maps were given to the British Library; the military maps were kept by George IV for his own use. “Not all of them were collected by George III in the first instance: like most collectors, he not only purchased individual items but also acquired the collections of others.” [Tony Campbell]
Update, 22 Apr 2020: From February, Smithsonian Magazine’s coverage.