Alex - here is what I found at a couple of websites (urls shown). It also appears that his father (also George Erving) identified below as a loyalist, was barred from returning to Massachusetts after the Revolutionary War. Interesting that the son was able to take these diplomatic posts - I wonder if the archives in London hold any secrets on him?
ERVING, George William (1769-1850)
Born in Massachusetts, brought up in London and educated at Oxford, he was the son of George Erving and Lucy. Although his father and grandfather were loyalists, GWE became an enthusiastic Jeffersonian and visited JM at Montpelier as early as 1800. His long diplomatic career included legation secretary and charge d'affaires at Madrid in 1804, Minister to Copenhagen, 1812-1813, and Minister to Spain 1814-1819, after which he retired from public life.
George W. Erving
ERVING, George W., diplomatist, born in Boston, Massachusetts, in 1771; died in New York City in July 1850. He was a son of George Erving, who, during the Revolutionary war, went to Halifax and thence to London, and sent his son back to the United States after educating him at Oxford. Mr. Erving was made consul at London by President Jefferson, and in 1804 was appointed secretary of legation to Spain, where he remained for six years. In 1811 he was commissioned special minister to Denmark, and charged with the subject of spoliations committed under the Danish flag on the commerce of the United States. From 1814 till 1819 he was United States minister to Spain.
Edited Appletons Encyclopedia, Copyright © 2001 VirtualologyTM