CREATE TABLE table_26591309_2 (first_broadcast_uk___bbc_four__ VARCHAR, official_tns_gallup_ratings VARCHAR)

When was the first UK broadcast for the episode with an official TNS Gallup rating of 1575000?
SELECT first_broadcast_uk___bbc_four__ FROM table_26591309_2 WHERE official_tns_gallup_ratings = 1575000
SELECT "first_broadcast_uk___bbc_four__" FROM "table_26591309_2" WHERE "official_tns_gallup_ratings" = 1575000