From the most Westward longitude (edge of Cornwall) to the most eastward longitude (East England) the width is 520km.
Note however that Cornwall is a rather small area of land that
protrudes quite far west, and East England protrudes a little to the
east. In addition England has a gradual taper to the north. On average
England is only around 200km in width.
Note however that Cornwall is a rather small area of land that
protrudes quite far west, and East England protrudes a little to the
east. In addition England has a gradual taper to the north. On average
England is only around 200km in width.