The Camperdown elm wouldn't exist had it not been for David Taylor. In Scotland around 1840, working as the Earl of Camperdown's head forester, he discovered a mutant contorted branch in the forest. The first Camperdown elm was cultivated by grafting the branch to the trunk of a Wych elm (Ulmus glabra).
(peeking under the canopy)
Every Camperdown elm in the world is from a cutting of that original tree. Cuttings are usually grafted onto Wych elms, but other grafting stock can be used, including Dutch elm, Siberian elm, and English elm.