CREATE TABLE table_1318 ("Episode" FLOAT, "Title" TEXT, "Story" TEXT, "Adapted by" TEXT, "Director" TEXT, "Airdate" TEXT, "Exists?" TEXT)

Name the msot episode that was adapted by leon griffiths
SELECT MAX("Episode") FROM table_1318 WHERE "Adapted by" = 'Leon Griffiths'
SELECT MAX("Episode") FROM "table_1318" WHERE "Adapted by" = 'Leon Griffiths'