It's Dark Outside (1964)

This spin-off from The Odd Man (1962) starred William Mervyn as the acerbic Inspector Rose, who, alongside the soft-hearted pensive Det. Sgt. Swift (Keith Barron), are joined by Anthony (John Carson) and Alice Brand (June Toblin), a barrister and his journalist wife, though not for long.

By the second season, the Brands and Swift departed, leaving the calm, cold Rose in prime position, supported by newcomers DS Hunter (Anthony Ainley), his girlfriend Claire (Veronica Strong), and her boozy reporter friend Fred Blaine (John Stratton).