Alec Guinness did not receive an Oscar nomination, despite winning NBR, for portraying the D'Ascoyne family including the Duke, the Banker, the Parson, the General, the Admiral, Young Ascoyne, Young Henry, and Lady Agatha.
There is also the Admiral and the General who are probably the closest in style which makes sense considering they are both military men. In both cases Guinness plays a controlled aspect to the men fitting of their profession they are proper in stance and manner even as older men. Both are fairly quick characters but in it just enough for a very amusing moment for each of them to have. Guinness is great as the firm Admiral who keeps his proper stance as he barks a foolish order that causes his ship to crash,. Guinness makes the fact that Admiral chooses to stay on board, despite everyone else safely leaving , especially hilarious thanks to that same steadfast expression on his face as the Admiral slowly sinks underwater while giving a salute.
The least special of Guinness's performance here is definitely that of portraying Agatha D'Ascoyne, that is because he does not even get a line and this one is mostly based on the visual of Alec Guinness in a dress. Guinness still gives it his all in his portrayal of Agatha. He is quite funny though in his expressions still when he shows great glee in Agatha as she smashes windows, or flies in a hot balloon to promote her feminist cause. Her appearance is brief and asks the least of Guinness, but he still handles it especially well since he doesn't choose this time to ridiculously overact or anything else. He still goes about being funny through the character even in this briefest of circumstances.
Guinness gives a remarkable set of performances in this film and it is unlikely that any actor could have handled this set of roles as well as Guinness does. What is so incredible about this performance is the way he manages to be visible and invisible in the role. Although it is obvious the film wants us to know Guinness is playing everyone, as there is a scene that pans from one D'Ascoyne to the next, Guinness manages to fully invest himself in each character making each of the D'Ascoyne's their own. He is able to become each character with a outstanding degree of ease considering the circumstances, and having each of the characters stand out in the way they need to through his stunning ability to create a particular voice and physical style for each. This is a great great great great great great great great performance by Alec Guinness as he succeeds with this very large challenge well making it look easy the entire time.