SOLUTION to General Knowledge No. 2590:

Across - 1, Pythagoras 7, Corm 8, Thalamus 9, Turner 10, Accord 11, Hoopoe 13, Phoebe 15, Mauser 18, Reggae 20, Queequeg 21, ITMA 22, Prince Igor Down - 1, (John) Profumo 2, Timon 3, Astarte 4, Omaha 5, Ajaccio 6, Suir 12, Pasteur 13, Perigee 14, Braemar 16, Alum 17, Rouen 19, Grieg.