At other times, magic and technology do develop in tandem; this is most common in the alternate history genre. Patricia Wrede's "Regency" fantasies include a Royal Society of Wizards and a technological level equivalent to the actual Regency; Randall Garrett's "Lord Darcy" series, Robert A. Heinlein's "Magic, Incorporated", and Poul Anderson's "Operation Chaos" all depict modern societies with magic equivalent to twentieth-century technology. In "Harry Potter", wizards have magical equivalents to non-magical inventions; sometimes they duplicate them, as with the Hogwarts Express train.