Day-Lewis may in fact give the ultimate Edwardian portrayal as the genius of this performance is quite extraordinary. Day-Lewis becomes the man of the time with every facet of his performance. His physical manners all are that of a man of perfect refinement who has tries to have the best tastes in all things. The way he turns pages in a book the way he walks they are all in that of a man who has learned to be as proper as one could possibly be. His voice only follows suit with his prissy high pitched voice that is perfect for his endless recitation of the books that he reads. The whole demeanor and every manner reinforces the idea of the repressed nature of the man's upbringing and life. It is to such an extreme in Day-Lewis that there is a strong comedic value actually in his work in that is rather quite funny because Cecil just is just so very proper. Although Day-Lewis slyly makes this a comic performance that does not mean he seems out of place in the film.
One of the amazing aspects of his work is that even though he allows some of what he does to be amusing that does not mean he does not realize Cecil as a real man. All he does still feels completely natural to the setting and he comes off enough as a realistic man of the period still. All of the mannerisms are used by Day-Lewis to create a cohesive whole that is Cecil Vyse. This is not just a great performance in terms of character creation though, Day-Lewis goes beyond that with his performance. Although he definitely plays Cecil Vyse as a repressed man and even technically speaking a boring one, he does not portray him as a simple man particularly in regards to Cecil relationship with the Lucy Honeychurch (Helena Bonham Carter). Although the story of picture suggests that Cecil is the wrong suitor and the "free-spirited" George Emerson (Julian Sands) is the right one, Day-Lewis's performance kind of rejects this notion.
Where Julian Sands plays his role so one note that he makes George rather uninteresting, Day-Lewis never makes that the case for Cecil. Cecil is a man who suffers from everyone else apparently telling him who he is in fact Lucy does a little too often. Day-Lewis though portrays an honest frustration in Cecil over her dismissive attitude, but he effectively shows it as something that he still needs to repress by his nature. Another strong example of the subtlety he brings is also when George is fairly obviously trying to woo Lucy while she is suppose to betrothed to Cecil. Day-Lewis again in these scenes suggests an underlying unease and that Cecil actually is aware of the situation but can break his mold to do anything about it. Day-Lewis's best scene though is when Lucy breaks off the engagement with Cecil. Day-Lewis makes it a surprisingly moving scene because he shows that Cecil is heartbroken over it, but Day-Lewis only allows it to be seen in a internalized fashion which properly fits Cecil's manner toward life. This is a perfect portrayal by Day-Lewis as he makes the boring character entertaining, and realizes his character fully as his own man rather than just a hurdle between the main romance.