With YSL in neon lights attached to a crane on a chaotic building site, the message could not have been louder or clearer. Yves Saint Laurent was being re-built by its latest designer: Anthony Vaccarello.

And by the time the audience was installed under a tranquil stone archway and the first model appeared in a corseted leather dress with curvy wide shoulders and a thigh-high skirt, Vaccarello's message was as clear as the YSL in sparkly dangling earrings. Except that the logo had been re-branded as Youthful Sexy Leather.

Add audacity from the Belgian/Italian designer, who has put his own brand on hold while he takes over from Hedi Slimane, and the show got spring/summer 2017 off to a racy start.

“To have fun" was the answer from the designer backstage when I asked him for his main message. He could have added all sorts of comments about taking on the name of a fabled designer. But it was obvious that Vaccarello, 34, in his mind's eye, took as a starting point where Yves Saint Laurent himself had morphed from daring young designer breaking the codes of good taste into a feted establishment figure. 

So it was back to the 1980's: brash, bold and mostly dressing for the night. The same curvy leather undulating across the breasts re-appeared with a pair of taut, rolled-up jeans. Although in his obsession with leather Vaccarello caught some of the fashion vibes of the moment, especially fashion's ubiquitous Henry VIII leg o'mutton sleeves.

The new designer can certainly cut like a French butcher: precise but delicate. Whether it was a V-neck to the waist in liquid, gleaming leather or a 'onesie', the fit was perfect.

As seen reflected in the catwalk's mirrored ceiling, the codes of Yves Saint Laurent were deftly noted. Tuxedo - tick; bosoms lightly veiled in black chiffon - tick.

What was added to the YSL archive? Bad taste. Where Hedi Slimane's young girls from the outskirts of LA seemed like teen innocents, Vaccarello's version was a knowing, attention-seeking nighttime-embracing woman. Will the silver glitter pastor that covered one nipple of a cut-away leather mini dress go on sale in YSL stores? Along with the orange cord dangly earrings from Yves's 'Opium' Chinese period? 

Where the new designer scores over the last is in his assured contouring of the female body. The designer's riffs on Le Smoking, the French word for tuxedo, were knife edge cuts and an-all-in-one outfit.

At the dinner, hosted by Francois Henri Pinault after the show, the executive said to me: "Anthony was the first person who came into my mind. The only one."

So with approval from Pinault, Vaccarello intensified the sexiness. Just when you thought that this dance-the-night-away, leather-uniformed woman must come up for air, she appeared in what might pass as daywear - a velvet jacket that looked like it had an earlier life as a Moroccan rug. 

 That, and denim, brought the show briefly into the reality of dressing for work, as well as play. The final stab at something faintly classy was a leopard print top sliced over one shoulder. 

Vaccarello was smart not to make his launch at YSL a tentative homage to a mythical fashion creator - even though some of the collection seemed like a homage to his previous job with Donatella Versace's Versus line.

The question is: did the new designer get to the essence of Yves Saint Laurent - and will he be able to keep up with the dramatically successful sales of Hedi Slimane? 

Vulgarity is currently something in what the French call "l'air du temps". Vaccarello's skill was not in keeping up with the Kardashians, but in presenting his collection with an exuberant, witty energy. 

But surely he should follow a different aspect of the rich YSL archive next season.  

No bared bosoms perhaps? What was shocking in the era of Yves, is now a big fashion yawn.