Dee posited a formal claim to North America on the back of a map drawn in 1577–1580; he noted that "circa 1494 Mr. Robert Thorn his father, and Mr. Eliot of Bristow, discovered Newfound Land." In his "Title Royal" of 1580, he invented a claim that Madog ab Owain Gwynedd had discovered America, intending thereby to boost England's claim to the New World over that of Spain's. He also asserted that Brutus of Britain and King Arthur, as well as Madog, had conquered lands in the Americas, so that their heir, Elizabeth I of England, had a prior claim there.