The enigma is that, although there are fourteen variations on the "original theme", there is another overarching theme, never identified by Elgar, which he said "runs through and over the whole set" but is never heard.
O enigma consiste en que, malia as catorce variacións no «tema orixinal», hai outro tema completo, nunca identificado por Elgar, do que di que «percorre toda a obra» pero nunca se percibe.