The series was originally intended to be a prequel to Ray Donovan. In February 2024, Paramount+ released the premise of the series, which was to be titled the Donovans, stating, "With the most powerful clients in Europe, The Donovans will see family fortunes and reputations at risk. Odd alliances unfold, and betrayal around every corner; and while the family might be London's most elite fixers today, the nature of their business means there is no guarantee what's in store tomorrow." The story was believed to be centered around Ray Donovan's character, which would explore the rise and formation of his criminal enterprise. Guy Ritchie was named as the director and executive producer. In October 2024, Paramount+ announced that the spinoff idea was called off and the show was rewritten to become its own standalone series with no narrative connection to Ray Donovan. Guy Ritchie remained on the creative team.
Pierce Brosnan and Dame Helen Mirren both appeared in The Long Good Friday (1980) but did not share any screen time together. Mirren played gangster moll Victoria to Bob Hoskins' Harold in the earlier feature, and here she portrays matriarch wife Maeve to Pierce Brosnan's crime boss Conrad Harrigan.
Tom Hardy's use of a 2024 Audi RS6 in the series is a likely nod to Layer Cake (2004) where he is part of a team that use an older version of the Audi RS6 vehicle.