Title Whitehall 1212 refers to phone number of Scotland Yard, because even though it was fully American radio show all of the scripts (supposedly) were based on true crime cases from Scotland Yard archives. Hosted by Chief Superintendent John Davidson, who actually was curator of the Black Museum, a collection of memorabilia kept in the Scotland Yard, each week show was presenting different case, most of which were in later years proved to be actual true crime stories.
Actually there was also a radio show called The Black Museum, hosted by Orson Wells, which was based on more or less same set of cases, but the two shows had slightly different approach. In Whitehall 1212 whole story was told from perspective of policemen, who try to solve the case, while The Black Museum was trying to recreate the crime itself and wonder into the dark corners of killer’s mind.
In total 44 episodes were produced, which were broadcasted between November 1951 and September 1952.