[1][3] He worked in films in various minor capacities for his idol Don Siegel,[1] and then on The Long Ships (1964) for Jack Cardiff and Genghis Khan (1965) for Henry Levin.

He subsequently went to work in Italy for producer Paul Maslansky on Castle of the Living Dead (1964), and then as director and co-writer of The She Beast (1966), which contains a witch hunt resembling the opening of Witchfinder General.

According to Tom Ryall, "[d]espite its low budget, Reeves was able to draw on fine performances from Boris Karloff and Catherine Lacey as old people who become obsessed with the violent sexual possibilities created by the permissive society, and Ian Ogilvy as the young man who becomes their unwitting tool.

[6] Made on a modest budget in East Anglia and adapted from the novel by Ronald Bassett, Witchfinder General tells the story of Matthew Hopkins, the lawyer-turned-witchhunter who blackmails and murders his way across the countryside.

[7] Reeves wanted Donald Pleasence to play the title role, but American International Pictures, the film's co-financiers, insisted on using their resident horror star Vincent Price instead.

The coroner's report stated that Reeves's death (from a barbiturate overdose) was accidental, the dosage being too marginal to suggest intention.