In The Legend of Hell House, the English investigators approach a mansion that was filmed at Wykehurst Park in East Sussex. In Matheson's novel the house was in the U.S. in Maine, and investigated by Americans.

Although the film was released in the U.S. with a P.G. rating, in the U.K. it was originally slapped with an X – and this despite the fact that Matheson's script significantly cut back on the graphic sexuality that was in his book.

The embalmed corpse of Emeric Belasco is played by veteran British actor Michael Gough (American audiences might recognize him as Alfred Pennyworth from Tim Burton's Batman, 1989).

The electronic soundtrack was provided by two composers: Delia Derbyshire and Brian Hodgson, whose background was in the BBC Radiophonic Workshop. Derbyshire engineered the first Doctor Who theme from a composition by Ron Granier.

In regards to former child actor Roddy McDowall, The Legend of Hell House was made between his appearances in two of the popular Planet of the Apes movies - Conquest of the Planet of the Apes (1972) and Battle for the Planet of the Apes (1973), and on Hell House he was joined by another former child actor: Pamela Franklin (from The Innocents, 1961).

The tales of hedonism and debauchery behind Hell House were loosely based on stories surrounding Satanist Aleister Crowley.

by Pablo Kjolseth

SOURCES:
Wikipedia
IMDB
The Legend of Hell House (1973) – go in, or don't! by Mark A. Hodgson, Black Hole DVD Reviews