Mayo as Lady Barbara Wellesley Robert Beatty as First Lieutenant William Bush Terence Morgan as Second Lieutenant Gerard Moultrie Kelsall as Third Lieutenant Crystal James Kenney as Midshipman Longley James Robertson Justice as Seaman Quist Denis O'Dea as Rear Admiral Sir Rodney Leighton Richard Hearne as Polwheal Michael J. Dolan as Surgeon Gundarson Stanley Baker as Mr. Harrison Alec Mango as El Supremo/Don Julian Alvarado Christopher Lee as the Spanish captain of the Natividad Diane Cilento as the voice of Maria, Hornblower's wife Alan Tilvern as Admiral Don Jose Hernandez John Witty as Captain Entenza Jack Watson as Capt. Sylvester (uncredited) Alexander Davion as Spanish officer (uncredited) Casting Warner Bros. acquired the film rights to the first three Hornblower novels – The Happy Return, A Ship of the Line, and Flying Colours – as a star vehicle for Errol Flynn when they were first published. For reasons that may have included the financial failure of the 1948 Adventures of Don Juan, the growing difficulties of working with the actor, and/or his advancing age, Flynn was not cast. Warner's was already building up Burt Lancaster as their new swashbuckling screen star, but the role of a British sea captain seemed to be outside his range, so Peck was ultimately cast on a loan-out from David O. Selznick, who received screen credit in the opening titles. Virginia Mayo was only cast after a number of high-profile British actresses were either not free or not interested. Peck's personal choice was Margaret Leighton. Studio head Jack Warner found Virginia Mayo more attractive. Production The film was shot at studios inside the United Kingdom, on Mermaid Street in Rye, East Sussex, at and also on location in France. El Supremo's Fortress is Fort de Brégançon in France. To save costs, the Hispaniola set from the 1950 Disney film adaptation of Treasure Island was reused as the frigate HMS Lydia. Instead of moving the horizon background in order to simulate movement on the water, the ship itself was rocked. This caused many problems because of the combined weight of ship, crew and equipment. The Italian brigantine Marcel B. Surdo represented the Witch of Endor for all at-sea exterior footage. The Marcel B. Surdo would also appear in such seafaring films as The Crimson Pirate, The Master of Ballantrae, and John Paul Jones. The explosive and fire effects were supervised by Cliff Richardson. Premiere and reception The