Who directed the episode viewed by 7.35 million?
CREATE TABLE "table1_21369888_4" (
  "episode" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "originalairdate" text,
  "viewing_figures_millions_sourced_by_barb_includes_itv1_hd_and_itv1_1" text
);
SELECT "directed_by" FROM "table1_21369888_4" WHERE "viewing_figures_millions_sourced_by_barb_includes_itv1_hd_and_itv1_1"='7.35';