It has been said that no one ever understood the question which is known by the name of the Schleswig-Holstein question — that the only person who got nearly to understand it was a German professor, and that it had driven him mad.
Source, in full
Speech at the annual dinner connected with the Christmas Horsham Cattle Show, held in the Black Horse Inn, Horsham, on 9 December 1863; quoted in "MR. SEYMOUR FITZGERALD, M.P., AND MR. CAVE, M.P., ON FOREIGN AFFAIRS." 11 December 1863 Evening Standard (London) p. 2 col. 2
Notes from Wikiquote
Compare Henry Temple, 3rd Viscount Palmerston#Misattributed