CREATE TABLE table_43291 ("Date" TEXT, "Time" TEXT, "Channel" TEXT, "Running Time" TEXT, "Notes" TEXT)

What is the running time of the transmission on bbc four channels on 23 March 2008?
SELECT "Running Time" FROM table_43291 WHERE "Channel" = 'bbc four' AND "Date" = '23 march 2008'
SELECT "Running Time" FROM "table_43291" WHERE "Channel" = 'bbc four' AND "Date" = '23 march 2008'