At his death, King George III had a collection of some 50,000 maps, plans, illustrations and related ephemera. The military maps were kept by his son George IV; earlier this year more than 2,000 of those maps were posted online by the Royal Collection Trust. But the vast majority went to the British Library, where it makes up the King’s Topographical Collection (“K.Top”). The collection is wide-ranging and diverse—George III was a bit grabby when it came to maps—and includes maps made from 1540 to 1824; it also, famously, includes the Klencke Atlas.
For the past few years the Library has been engaged on a project to digitize the 40,000 items of the Collection; last month they announced that the first batch—some 18,000 images—has been released to Flickr—see this Flickr album—where they may be freely accessed and downloaded.