CREATE TABLE table_203_397 (id DECIMAL, "series" TEXT, "launch date" TEXT, "finale date" TEXT, "days" DECIMAL, "housemates" DECIMAL, "winner" TEXT, "main presenter" TEXT, "grand prize" TEXT, "liveshow\ audience\ millions" DECIMAL)

who has presented the most seasons ?
SELECT "main presenter" FROM table_203_397 GROUP BY "main presenter" ORDER BY COUNT("series") DESC LIMIT 1
SELECT "main presenter" FROM "table_203_397" GROUP BY "main presenter" ORDER BY COUNT("series") DESC NULLS LAST LIMIT 1