The series takes its name from characters who appeared in Arthur's written works, named the Baker Street Irregulars. These characters, young boys who Sherlock uses on the streets of London to gain intelligence while carrying out his investigative work, are featured in three stories alongside the famous detective.
The term "Baker Street Irregulars" comes from the title of Chapter 8 in The Sign of the Four. In that novel, Holmes enlists the Irregulars in tracking the progress of a boat on the River Thames.
Some scenes were filmed at Liverpool's Stanley Dock, England, the same location used for Peaky Blinders - Gangs of Birmingham (2013) Captain America: The First Avenger (2011) and Robert Downey Jr.'s Sherlock Holmes (2009).
There were some disturbing moments behind the scenes as JoJo says he was followed around by birds. The actor said: "Memorable moments - lots of bird action. Birds were haunting me through the whole of the shooting process, multiple times, pigeons flying in, sitting on lights, come sweeping past my shoulder. Our studio, most of our stuff is on location, but the studio we had in Liverpool was infested with seagulls. I don't know if they were resting on the roof or inside. At one point, a seagull got in my hotel room, I got nits off a chicken at one point. Birds literally haunted me throughout the production."
Filmed in various locations in the Cheshire county in 2019 and 2020. In January 2020, scenes for The Irregulars were filmed in Abbey Square in Chester, a Victorian house in Hoole, and at the National Waterways Museum in Ellesmere Port just before the start of lockdown in March 2020, when filming had to be suspended. Then in August 2020, filming resumed and returned to Ellesmere Port to the National Waterways Museum.