Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21855 ( "Episode" real, "Original title" text, "Directed by" text, "Written by" text, "Original airdate" text, "Duration" text, "Viewership" text )

### Question ###
Who was the director when the writer was John Sullivan?

### Accurate SQL ###

SELECT "Directed by" FROM table_21855 WHERE "Written by" = 'John Sullivan'