Part of this film was shot in buildings around St. Catherine's Dock near Tower Bridge in London, one of which was rented out as studio space for artists and film-makers by a company known as S.P.A.C.E., an acronym for Space Provision (Artistic, Cultural and Educational) Ltd.
The same location was used by Dutch sculptor
Herman Makkink and his brother Cornelis for their studio, and several scenes in Drop-out show art pieces which were later prominently featured by
Stanley Kubrick in
Arancia meccanica (1971) -- the most easily recognizable are Herman's phallic-shaped sculpture called "Rocking Machine" (used as the murder weapon in The Cat Lady scene) and Cornelis' "Christ Unlimited" figures (which appear in Alex De Large's apartment). Nine paintings by Cornelis were also used by Kubrick (a detail of one, featuring a woman with her legs spread, hangs over Alex's bed and the rest appear on the walls of The Cat Lady's studio).
Although Drop-out is extremely hard to see these days, publicity stills from the film featuring
Vanessa Redgrave and other cast members next to these pieces of art are relatively common.
Some speculate that Kubrick stole the idea to use the artwork from seeing Drop-out, which was released one year before A Clockwork Orange, but Herman Makkin said that Kubrick and his wife visited his studio as early as 1969 so the fact that both films feature the same art is probably just a coincidence and a testament to Makkin's futuristic vision.
