CREATE TABLE table_name_51 (replaced_by VARCHAR, date_of_vacancy VARCHAR)

who is the replacement when the date of vacancy is 1 september 2008?
SELECT replaced_by FROM table_name_51 WHERE date_of_vacancy = "1 september 2008"
SELECT "replaced_by" FROM "table_name_51" WHERE "1 september 2008" = "date_of_vacancy"