How many number in series's are written by Greg Haddrick?
CREATE TABLE "table1_21666472_1" (
  "no_in_total" text,
  "no_in_series" text,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text
);
SELECT COUNT("no_in_series") FROM "table1_21666472_1" WHERE "written_by"='Greg Haddrick';