Whenever a British TV show, usually a crime series, refers to the phrase "Softly, Softly", it's not a reference to the venerable crime drama. Instead, within the reality of Toobworld, it's a reference to a style of police interrogation in which the suspect is treated with kid gloves, or just in treading carefully during an investigation.
The full phrase is "Softly, softly, Catchee Monkey." And that was heard in the TV shows 'Kingdom' and 'Ashes To Ashes'.
Just so you know.....