Bulldog Drummond is an historical fictional character referenced in "Family Limitation". The Bulldog Drummond stories follow Captain Hugh "Bulldog" Drummond, D.S.O., M.C., a wealthy former WWI officer of the fictional His Majesty's Royal Loamshire Regiment, who, after the First World War, spends his new-found leisure time as a private detective. The character appears in a series of novels by "Sapper", a pseudonym of Herman Cyril McNeile. Only the first book, named "Bulldog Drummond", had been published at the time the episode is set.
The novel begins with ex-British Army Captain Hugh "Bulldog" Drummond, a wealthy former World War I officer of the Loamshire Regiment, dashing and strong, but not handsome, placing an advertisement in The Times stating his desire for an adventure. He receives a reply from a young woman, concerned about some business acquaintances of her father. It turns out that her father is being blackmailed by archvillain Carl Peterson who is attempting to organise a coup d'état to enable a pro-communist takeover of Britain. Ironically, this is being done for financial gain as Peterson is being paid by wealthy foreigners who will profit from this. Drummond is captured several times, but manages to escape before eventually defeating Peterson and his henchmen with the aid of ex-army friends.