The City of London Heliport is partially constructed from the remains of Stingray (1964)'s Marineville Tower.
The fictitious prison named Parkmoor would later be mentioned in Crown Court episodes Crime In Prison [14-16/2/73] and Intent To Kill [9-11/5/73]
This marks the only use in the series (or any of the Supermarionation series of Puppet films) of a real human face (or, at least part of one), when Lady Penelope peeps through the front entrance door of the Bank of England.
Footage of a real owl is seen for a brief moment as Parker and Lady Penelope begin their outdoor conversation.
Costumer Elizabeth Coleman was once again on point, providing the older traditional British prison uniform, stamped with its characteristic pattern of arrows.