Typical British prejudice, also in the article ...
1) He was not found behind the "British lines", but behind the Allied lines.
2) If he is found behind Wellesley's lines, that makes about 35% chance that he was British, 25% that he was Dutch, and 40% chance that he was some kind of non-Prussian German.
History schoolbooks in Britain seem to be written by Bernard Cornwell ...