CREATE TABLE table_204_349 (id DECIMAL, "year" DECIMAL, "conservative\ councillors" DECIMAL, "labour\ councillors" DECIMAL, "independent\ councillors" DECIMAL, "liberal\ councillors" DECIMAL)

the only year with 10 conservative councillors was when ?
SELECT "year" FROM table_204_349 WHERE "conservative\ncouncillors" = 10
SELECT "year" FROM "table_204_349" WHERE "conservative\ncouncillors" = 10