CREATE TABLE table_12221135_3 (arrival VARCHAR(255), operator VARCHAR(255), calling_at VARCHAR(255))
How many trains call at Castor, Overton, Peterborough East and are operated by LNWR?
    
SQL: SELECT COUNT(arrival) FROM table_12221135_3 WHERE operator = "LNWR" AND calling_at = "Castor, Overton, Peterborough East"