Mansfield was born in Berlin and spent his early childhood on Heligoland, Germany, an island in the North Sea, then under British rule.
His parents were Hermine Küchenmeister-Rudersdorf, a Russian-born operatic soprano, and Maurice Mansfield, a British London-based wine merchant (died 1861).
He played several further roles in London and then travelled to America in 1882, where he made his Broadway debut as Dromez in Bucalossi's Les Manteaux Noirs with a D'Oyly Carte touring company.
[3] Mansfield then appeared in Baltimore, Maryland, with another D'Oyly Carte troupe, as the Lord Chancellor in Gilbert and Sullivan's Iolanthe in December 1882.
Mansfield's portrayal of Chevrial, a "realistic exhibition of depravity in dotage, by a young and comparatively unknown actor, was a surprise to the public, the managers, and the critics, and soon became a town topic.
"[1] He next played the role of Ko-Ko, the Lord High Executioner in The Mikado, in Boston in early 1886, his last production with a D'Oyly Carte cast.
[6] He was one of the earliest to produce George Bernard Shaw's plays in America, appearing in 1894 as Bluntschli in Arms and the Man, and as Dick Dudgeon in The Devil's Disciple in 1897.
[5] He began the new century on Broadway in the title role in King Henry V (1900), followed by the title character in Monsieur Beaucaire, Brutus in Julius Caesar (1902), Karl Heinrich in Old Heidelberg (1903 and 1904), and roles in Ivan the Terrible (1904), A Parisian Romance (1904 and 1905), The Merchant of Venice (1905), Richard III (1905), Alceste in The Misanthrope (1905), The Scarlet Letter (1906) and Don Carlos (1906), among others.
One frightened theatre-goer wrote to the police accusing Mansfield of the murders because he could not believe that any actor could make so convincing a stage transformation from a gentleman into a mad killer without being homicidal.
Mansfield attempted to gain public favour and stem the criticism that he was receiving by offering a performance of the comedy Prince Karl for the benefit of the Suffragan Bishop of London's home and refuge fund for reformed prostitutes.