And with motherly advice like that, how could anything go wrong?

In "The Duchess," Georgiana of London (a lovely and utterly regal Keira Knightley) has been noticed, plucked from obscurity by the Duke of Devonshire before she is 18. Along with her delightfully position-crazed mother (a proper, convincing Charlotte Rampling), Georgiana cannot believe her own good fortune. Alas, royalty can be deceiving.

The cool, menacing Duke of Windsor (a formal and perfectly cast Ralph Fiennes) is distant and dismissive. Beyond needing a woman for show at formal events, he hasn't much respect for marriage or its trappings.

Although pledged to produce a male heir, Georgiana fails twice, bearing daughters, before she finally produces a son.

Yet her husband remains overbearing and insensitive, at least to Georgiana. Pursuing other women as if they were battle conquests, he taunts his seething bride and makes it clear he is far from thrilled at her frequent dabbling in public affairs and gambling.

Active in politics -- well, as active as a woman could get in the 1770s -- Georgiana openly questions the prevailing law of freedom for some, dismissing the concept as an "either/or," and likening it to someone being dead or loved. Neither, she observes, can be achieved in moderation.

Growing more confident and outspoken as her marital woes deepen, Georgiana becomes known as the "empress of fashion" and is ultimately tempted by a dalliance of her own. To distract herself, she uses her popularity and feminine wiles to influence elections. One candidate in particular, Charles Gray (a smoldering and dashing Dominic Cooper) fancies her, which only serves to make their game of resistance more exciting.

When her husband's mistress (a sweetly subjugated Hayley Atwell) pleads with her that there are "no limits to what we must do for our children," Georgiana tries to hang on to her pride and realizes that any shred of secrecy, never mind decorum, has been destroyed.

Georgiana, rarely unsure of herself and palpably desperate, is told she needn't please others all the time. But she meekly replies to the contrary, "It's what I've been brought up to do." And for her righteous efforts, she pays a terrible price.

Alternately obedient, passionate and explosive, Georgiana sacrifices her own happiness for that of her children. She is a Spencer, and the future she forsakes makes her selflessness all the more timeless. The similarities with Diana, her princess descendant two centuries later, are both eerie and tragic.

Crossing any lines of class and heritage, the themes persist today: a woman's place, children above all else, and heartbreak when one's chance for true love is trampled or, worse, forbidden.

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