"In all important matters, style, not sincerity is the essential,” wrote Irish dramatist Oscar Wilde. He might have been talking about M. Gustave H, the fastidious concierge of The Grand Budapest Hotel pitch perfectly played in the new film by honorary Irishman Ralph Fiennes, probably best known for his turn opposite Liam Neeson in Schindler’s List.

Set in the fictional European nation of Zubrowka, the Grand Hotel is a five star resort where the tough yet charming Gustave H rules the roost and where fabulously rich widows often fall under his spell.

The 84-year-old dowager countess Madame Celine Villeneuve Desgoffe und Taxis (played by an almost unrecognizable Tilda Swinton) is one such example. Madame D is deeply in love with M. Gustave, and after her sudden and mysterious death he finds himself the sole inheritor of a priceless painting she owns called Boy With Apple.

But being absurdly rich, Madame D’s will is instantly contested by enough dubious relations to populate a small village. One of them is Madame D’s own treacherous son Dmitri (played with mustache twirling glee by Adrien Brody). Dmitri has no intention of seeing his inheritance carried off by a lowly concierge and so he sets his black-leathered psychopathic henchman Jopling (Willem Dafoe) on the case.

But before M. Gustave can even daydream about what his unexpected and newfound wealth will mean to him, he’s wrongly accused and imprisoned for the countess’ murder.

That leaves him dependent on his fanatically faithful lobby boy Zero to help him clear his name. Zero (played in a star-making turn by 18-year-old newcomer Tony Revolori) is already in love with Agatha (Saoirse Ronan) the pastry chef at the famous Mendl’s bakery, where she is famous for making the town’s favorite pastry the Courtesan au Chocolat.

Like M. Gustav and Zero, Agatha is also charming and a little damaged. She has a birthmark that looks like Mexico on her right cheek and she’s slow to trust, but unshakable when she decides to.

For Ronan it’s another opportunity to play a character that explodes expectations and whose quirkiness is a big part of her attractiveness. Although they are nothing alike, Ronan’s inspired turn as Eleanor in Niall Jordan’s terrific vampire feature Byzantium was an earlier opportunity to play another teenager with a teeming and unexpected inner life, the kind of role she handles with particular skill.

In The Grand Budapest Hotel Ronan, as well as taking part in a Wes Anderson film (a reward in itself) is stepping into the top tier of serious Hollywood actors. She knows it too.

“I kept thanking him (Anderson) while we were shooting because I couldn’t quite believe that he had asked me to be in it,” she told the press at the premiere.

“It’s just such an amazing group of actors to be involved with and the crew were fantastic so it was a real honor for me. When I went on set for the first time it truly felt like I was part of this Wes Anderson experience. Everything was so tactile and real and alive and it was quite a surreal moment.”

In the film Ronan is part of what could be called a love triangle. Zero is in love with her, she’s besotted with him, but both are besotted with the dashing M. Gustave, because how could you not be?

Fiennes is sensational in the role. His character is vain but deeply considerate, passionate but attentive to others, self-involved but sensitive, a mass of delightful and ultimately charming contradictions.

M. Gustave lives for love, and when that fails he lives for poetry and his own panache. Director Anderson, in creating this dashing character, had in mind the movie stars and capers of pre-Hayes code Hollywood.

Had this been 1933, Ivor Novello would have been ideal casting, but as it is Fiennes brings immense subtlety and feeling to scenes you will want to watch over and over between himself and his devoted lobby boy Zero.

It’s a remarkable balancing act, The Grand Budapest Hotel. The chocolate box European capital the filmmakers have created contrasts sharply with the rise of an increasingly fascist military, portending the charnel house that Europe is about to turn itself into.

Miraculously, Anderson’s light touch moves between the realities of history and the requirements of his hilarious grand hotel caper, in which everyone ahs a hidden motive that adds layer upon layer to the tale. It’s as brainy as his previous outings – actually it’s even more so – but it retains the power to move you deeply and unexpectedly when you’ve just convinced yourself it’s all a bit of a pantomime.

For Ronan it’s another triumph on her ascent to Hollywood superstardom. Her career trajectory has been so nimble and surefooted to date that it’s a marvel to behold. There’s no hint of the dysfunction or tantrums that bedevil other young actors.

Perhaps it’s her Irishness that serves as a counterfoil to all the smoke and mirrors of LA glamour. One thing’s for sure, she’s no one’s fool.

This week Ronan is filming Stockholm, Pennsylvania, a tense drama in which she plays the developmentally stunted Leia, a young woman raised by a kidnapper who now has to acclimatize to life with her actual parents after 20 years of separation.

Sex and the City’s Cynthia Nixon plays the girl’s grief-stricken mother, who goes to extreme lengths to recapture her daughter’s love and Jason Isaacs plays her captor.

We’ll next see Ronan in actor, writer and director Ryan Gosling’s How to Catch a Monster. The film tells the story of a single mother who is swept into a dark underworld, while her teenage son discovers a road that leads him to a secret underwater town.

Fans of writer Colm Toibin will be delighted to hear she’ll play the lead in the film of his most successful novel Brooklyn to be filmed in New York later this year. Helmed by Irish stage and film director John Crowley, who made Closed Circuit last year starring Ciaran Hinds, Ronan’s character Eilis is a young Irishwoman making the transition to a new world and a new sense of herself.

For Ronan it’s a nigh perfect role as she makes these kinds of transitions herself. As both an Irish and Hollywood actress, and as an Irish and American citizen, she’s particularly alive to the competing claims of the two worlds, and Toibin himself could hardly have wished for a more sensitive actress to embody the character.

But first we can savor Ronan as Agatha in The Grand Budapest Hotel. The chemistry between Ronan and Revolori is palpable, as is their respect and admiration for M. Gustave, their friend and mentor in a brand new tale that will make you laugh and break your heart, the way old movies used to when it opens on March 7.