Numerous country houses in the northern Greater London and Hertfordshire area were used for the external shots of the many mansions featured in the series. In the episode "For the Girl Who Has Everything", the exterior of Hilfield Castle in Aldenham was used for Kim Wentworth's (Lois Maxwell's) home. The Tudor-looking Edgwarebury Hotel on Barnet Lane in Elstree, now The Manor Elstree, was used in the episodes "Who Killed Cock Robin?" and "The House on Haunted Hill" and a plethora of other ITC series. The exterior of the Lambert Clinic in the comical episode "A Disturbing Case", written by Mike Pratt himself, is now the Institute of Grocery Distribution in Letchmore Heath, Hertfordshire. The Seaton Residence, a large white house with Doric columns at the front used in "The Smile Behind the Veil" episode is the Dyrham Park Country Club, the club house of a golf club in Galley Lane, Barnet. Woburn Abbey in Woburn, Bedfordshire, is featured in the episode "The Man from Nowhere" and is visited by Jeannie and a Marty imposter.