CREATE TABLE table_204_561 (id DECIMAL, "fence" DECIMAL, "name" TEXT, "jockey" TEXT, "age" DECIMAL, "handicap  ( st-lb ) " TEXT, "starting price" TEXT, "fate" TEXT)

which jockey is on top in age
SELECT "jockey" FROM table_204_561 ORDER BY "age" DESC LIMIT 1
SELECT "jockey" FROM "table_204_561" ORDER BY "age" DESC NULLS LAST LIMIT 1