The mood for the latest Lanvin show felt almost downbeat on arrival at the venue of the École des Beaux-Arts. That's downbeat in Lanvin terms, you understand, which is to say not very sedate at all by most established norms. As male ushers served popcorn, cans of soft drinks, and mini bottles of Champagne to the milling crowd, a casual, loose atmosphere was created. It was like a high-fashion fairground where you might bump into Catherine Deneuve playing pitch-and-toss.

This relaxed mood continued as the popcorn was swept up and the show began. Here day and night, night and day were all mixed together, sometimes in one look. The spirit was carefree yet elegant, controlled yet not giving a damn. There was an almost twenties feeling in the first dress, an idea of a floral appliquéd tracksuit in the second look, a fifties cocktail dress in the third…Each model reveled in an idiosyncratic appearance of her own, with makeup tailored to meet her individual needs and hair mostly tied back. In anybody else's hands, this could have been something of a mess; in Alber Elbaz's, it felt like freedom and fun.

A teenage atmosphere permeated the collection, a schoolgirlish view that avoided the saccharine and cute and could apply to all ages. This was most noticeable in the shoes: Gone were the ballet flats; in their place, a scaled-down version of a men's oxford. It was the sign that a much tougher girl was emerging for Elbaz this evening. She was no longer wearing prissy slippers, and her new footwear altered the entire silhouette. In one of the many standout looks, featuring a godet skirt and a top encrusted with winged insect appliqués and embroideries, the shoes transformed the meaning of such a mélange to one of a warped bobby-soxer. That was reinforced by the reams of thick gold chains, a constant motif in the collection, along with the letters that dangled from them. In this instance they spelled "cool." "There is no word I hate more than cool!" Elbaz declared after the show. Unusually for a fashion designer, Elbaz often starts his collections by contemplating spoken and written words; here, they were purposefully on display for all to see. The ones he does prefer are "love," "happy," and "help." And he wants us to pay attention to those words: "I think this is a collection about thinking," he explained. "It is about the world changing, women changing. Who's next? Which designer? Which pope? This is a collection that is not just a global view, but more a local view. How the skills of the French atelier are valid, precious, and relevant. How you can have fashion and business and not kill fashion."

This designer has always been adored personally, and now that personality is coming more to the fore in his output for the house. In Lanvin past, before the tenth anniversary point, there was much to admire. Now, with Elbaz's new, relaxed, yet almost contrary, teenage-spirited approach, there is much to love. And in case you need a reminder, you can read it on a necklace.