Quantos comboios fazem escala em Castor, Overton, Peterborough East e são operados pela LNWR?
CREATE TABLE table_12221135_3 (arrival VARCHAR, operator VARCHAR, calling_at VARCHAR)
SELECT COUNT(arrival) FROM table_12221135_3 WHERE operator = "LNWR" AND calling_at = "Castor, Overton, Peterborough East"