and A Prize of Arms.) Casting Alan Ladd had appeared in Warwick's first three films, and was discussed as a possible star. So too was Richard Widmark who ended up making A Prize of Gold for the company instead. When the British Admiralty was approached to co-operate it requested that Spencer Tracy play the lead. Eventually, José Ferrer was signed to star, with Terence Young to direct. Young arrived in Hollywood in October 1954 to discuss the film with Ferrer. At the time, Ferrer was considered a film star having appeared in the popular Moulin Rouge. He was also a renowned theatre director and had just directed his first feature, The Shrike (1955). By January 1955, it was announced that Ferrer would direct as well as star in The Cockleshell Heroes. Script The script was written by Bryan Forbes who was better known at the time as an actor. Forbes had been writing a lot of short stories and journalistic pieces, and had done some uncredited work on the screenplay for Warwick's The Black Knight. Forbes later said, "I got the reputation as a fast man with a pen, and as a result of that I got my first real screenplay assignment for Cockleshell Heroes." Ferrer had Forbes's script rewritten by Richard Maibaum, who had worked on several Warwick movies, which Forbes admitted "I didn't appreciate". Shooting Filming started in March 1955. Filming was done in Portugal and at several Royal Marine establishments, with the Commandant-General Royal Marines training the actors for drill and canoe handling. The training camp scenes in the film were shot at Eastney Barracks in Southsea, Hampshire. Many of the barrack buildings seen in the film still exist including the military buildings further up the beach where the scene to dispose of the live explosive device before its fuse time expired was filmed. The Royal Navy ships, and , were used to portray a German anti-submarine vessel dropping depth charges. This resulted in the ship dropping the first depth charges being seen with F383 on its side but in the next shot it has F384 on the side. The two corvettes were both scrapped shortly after filming (in 1956 and 1958 respectively). Studio scenes were shot at Shepperton. The limpet mine scenes were filmed in the King George V Docks in North Woolwich and many of the other scenes were filmed on the adjacent bomb sites