Originally projected as being Volume 3 (of 4), Brittania copies the text from Camden's Britannia and the maps from Speed.
In its day it (& he) was roundly condemned as a plagiarism. His later plates were no better.
Displayed scale of 5 miles = 33.5mm, or 3.8 miles/inch; scale actual = 5.0 miles/inch, or 1:315,000.
The maps are horribly drawn - very ugly in comparison to the productions from Amsterdam (Blaue & Jansson). Look at the dolphins, look at the badly executed text (quality and layout) in the cartouche. It's horrible.