Short answers, pulled from the story.
Emanuel Bowen was a Welsh map engraver born in 1694 at Tal-y-Llychau, Carmarthenshire. He became the only person to hold the title of Royal Mapmaker to both King George II of Great Britain and King Louis XV of France. He was regarded by his contemporaries as one of the leading London engravers by 1726.
Britannia Depicta was an atlas published in 1720, produced with John Owen, containing over two hundred road maps and a miniature county map of every county in England and Wales. A distinctive feature was that maps were engraved on both sides of each page, making the volume unusually compact and portable.
Bowen trained several prominent engravers, including Thomas Kitchin, Thomas Jeffreys, and John Lodge. He also trained his own son Thomas Bowen, born in 1733, who later collaborated with him on the Atlas Anglicanus published in 1767.
Bowen's A Complete Map of the Southern Continent depicted Australia and the surrounding region based on a chain of maps tracing back to Joan Blaeu's 1648 world map. The map drew a boundary between Hollandia Nova and Terra Australis at the 135th meridian East of Greenwich. When Britain established the colony of New South Wales in 1788, its territorial claim included all land east of precisely that meridian.
Bowen wrote two extended legends on the map. One defended the explorer Ferdinand de Quiros, whose account of lands east of Carpentaria had been called fiction, arguing the map itself proved him credible. The other called for British discovery and settlement of Terra Australis, comparing its latitudes to those of Java, Borneo, the Moluccas, Madagascar, and Peru to argue the continent must be equally rich.
Emanuel Bowen died on the 8th of May 1767 in poverty, a fate common among cartographers of his era despite his royal patronage. His son Thomas Bowen, born in 1733, continued the family business but also died destitute, in a Clerkenwell workhouse in 1790.