For you, Nan. Cut and pasted from various sources.
Originally meant as the first James Bond film, Thunderball was the center of legal disputes beginning in 1961. Former Ian Fleming collaborators Kevin McClory and Jack Whittingham sued him shortly after the 1961 publication of the Thunderball novel, claiming he based it upon the screenplay the trio had earlier written in a failed cinematic translation of James Bond.
The lawsuit was settled out of court; McClory retained certain screen rights to the novel's story, plot, and characters. By then, "James Bond" was a box office success, and series producers Albert R. Broccoli and Harry Saltzman feared a rival McClory film beyond their control; they agreed to McClory's producer's credit of a cinematic Thunderball, with them as executive producers.
Later, in 1964, EON producers Broccoli and Saltzman agreed with McClory to cinematically adapt the novel; it was promoted as "Ian Fleming's Thunderball". Yet, along with the credit to screenwriters Richard Maibaum and John Hopkins, the screenplay is also identified as based on an original screenplay by Jack Whittingham and as based on the original story by Kevin McClory, Jack Whittingham, and Ian Fleming.
To date, Thunderball has twice been adapted cinematically; the 1983, McClory-produced Never Say Never Again, features Sean Connery as James Bond, but is not an official EON production. (The title is based on a conversation between Sean Connery and his wife. After the film Diamonds Are Forever he told her he'd 'never' play James Bond again. Her response was for him to "Never say never again". She is credited at the end of the film for her contribution. As a result, it was the first Bond movie to use a non-Fleming originated title.)
The film For Your Eyes Only is noted for its pre-title sequence which sees the final comeuppance of Ernst Stavro Blofeld, Bond's enemy in five previous films. For this film, Blofeld is deliberately not named due to copyright restrictions with McClory, who owned the film rights to Thunderball which supposedly includes the character Ernst Stavro Blofeld, the organization SPECTRE, and a number of other material associated with the development of Thunderball. The demise of Blofeld was added to show that the "James Bond" series did not need Blofeld.