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_8 (year INTEGER, venue VARCHAR, event VARCHAR, result VARCHAR)

### Question ###
What is earliest year that had a 50km event with a 2nd place result played in London, United Kingdom?

### Accurate SQL ###

SELECT MIN(year) FROM table_name_8 WHERE event = "50km" AND result = "2nd" AND venue = "london, united kingdom"