The secluded location of Department S was filmed at the farm owned by producer Brian Clemens: Park Farm, Ampthill.
The railway station scenes were filmed at Stanbridgeford Station, Bucks. The station was demolished shortly after filming was completed.
The helicopter seen is a 1967 Hughes 300 (model 269B) construction number 670317. Re-registered as G-PLOW and it is still airworthy and flying in Britain.
The events of the episode take place on June 19th; Steed apprehended Gerard Kafka, head of Murder International, at noon seven years previously.