The film co-stars Alastair Sim, William Mervyn, Coral Browne, Harry Andrews, Carolyn Seymour, James Villiers and Arthur Lowe.

Jack, a paranoid schizophrenic, thinks he is Jesus Christ and shocks his family and friends with his talk of returning to the world to bring it love and charity, not to mention his penchant for breaking out into song and dance routines and sleeping upright on a cross.

Herder attempts to cure him through intensive psychotherapy, to no avail; Jack so thoroughly believes that he is the "God of Love" that he dismisses any suggestion to the contrary as insane.

Later on, at O'Toole's apartment, the deeply inebriated actor phoned his manager and said, "I'm with the crazy Hungarian and I know I'm drunk but I give you 24 hours to set this movie up."

Filmed at the sprawling estate of Harlaxton Manor, with the interiors reconstructed on sound stages, the production cost $1.4 million, with O'Toole working for free (he was instead paid a great deal for the big-budget Man of La Mancha, released by the same studio later the same year).

O'Toole begins where other actors stop, with the unfocused gaze, the abrupt bursts of frenzied high spirits and precipitous depressions.

Funny, disturbing, finally devastating, O'Toole finds his way into the workings of madness, revealing the anger and consuming anguish at the source.

In a review nearly 30 years after The Ruling Class was first released, Ian Christie said the film is "unashamedly theatrical, and it emerges from a particularly interesting period in English culture when theatre and cinema together were mining a rich vein of flamboyant self-analysis.

Many stage works of this period cry out for filmic extension—in fact, Medak had just filmed a very different play that mingled fantasy and reality by a writer often bracketed with Barnes, Peter Nichols’ A Day in the Death of Joe Egg.

Not only are there allusions to Shakespeare and Marlowe, but also to Wilde and Whitehall farce; to the gentility of Ealing Studios, with a plot that distantly evokes that other great black comedy Kind Hearts and Coronets, and to Hammer's gore-fests.