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_name_18 ( attendance INTEGER, league_position VARCHAR, opponents VARCHAR )

### Question ###
When in the 1st league position, how many people watch as they faced West Ham United?

### Accurate SQL ###

SELECT MIN(attendance) FROM table_name_18 WHERE league_position = "1st" AND opponents = "west ham united"