While there was indeed a German spy codenamed 'Trumpete' operating in Goa, he was a man named Robert Koch and both he and his wife Grete were kidnapped in 1942 by Colonel Stewart and Lieutenant Colonel Lewis Pugh and it's believed murdered in Castle Rock, Karnataka. The character 'Mrs. Cromwell' was purely invented as a romantic interest for Roger Moore's character. Similarly the character of Jack Cartwright was an invention for the film, although as noted below, the role of this character had a basis in fact.