"Dr No" was the first "James Bond" film to be released. It was not the first book to be released but the producers felt it was the perfect starting point for the series. Sean Connery was not approved by Ian Fleming, as he was Scottish and didn't match his idea of the real James Bond. Which Irish born, British actor, best know for playing British war heroes, did Ian Fleming want in the part?
Answer: Richard Todd
Richard Todd was a friend of Fleming who thought Todd was the right person to play Bond. Todd saw active service in WWII. In fact, after the war he turned to acting and played Major John Howard, who was Todd's superior in actual events in "The Longest Day" (1962)(Another actor played the role of Todd). It was while working on this movie, that a scheduling conflict meant he could not accept the "Dr No" role.
Cary Grant was the first choice of the producers but when he would only commit to one movie he was not considered to be the best choice. Roger Moore, "The Saint", was considered too young and Rock Hudson was never considered for the role.