Just off Sloane Square, in a building originally designed in 1889 by the Victorian architect Edwin Thomas Hall, the lavish new …At Sloane hotel has finally opened its doors to guests, following eight years of anticipation and six years of restoration and remodelling, which included adding an additional sixth floor with its own cupola to the listed building.

The hotel is a unique collaboration between the world-renowned hotelier Costes, the 300-year-old Cadogan, who manages 93 acres across Kensington and Chelsea, and French architect, designer and interior decorator François-Joseph Graf, one of the most revered names in interiors. 

Monsieur Graf’s phenomenal attention to detail is at play throughout the hotel, from the intimate lobby and seductive basement bar to the top-floor restaurant and the 30 remarkable bedrooms that lie between them.  

The sumptuous interiors were inspired by the grandeur of the British Empire when it was at its zenith, encompassing far-flung territories and countries like Hong Kong and then-Burma to Oman and Kenya, at the time when Mr Hall was designing the building and when a Grand Tour of Europe was still seen as a relatively exclusive ambition. 

The neo-Greek friezes and mosaics in the vestibule are a nod to this tradition and set the tone for soft check-ins in the lobby, which is more like an elegant private sitting room with a library, where guests are welcomed over tea, coffee or champagne, surrounded by a curated selection of books from local bookshops, including John Sandoe, Taschen, and the V&A Museum. 

During his meticulous research, Mr Graf discovered and fell in love with aspects of turn-of-the-century British craftsmanship, such as lights designed by William Arthur Smith Benson, pioneer of the Arts and Crafts lighting design, which Graf’s team of hand-picked artisans have faithfully recreated throughout …At Sloane, resulting in exquisitely lit spaces diffuse with the flattering glow of over 700 original and reproduction lamps. 

Inspired by Chelsea’s long association with the Arts and Crafts movement, the theme continues in the main stairwell, which has been papered with the grey and white organic maximalism of William Morris wallpaper. 

Mr Graf’s exacting standards and vision for …At Sloane were brought to life by a team of dozens of artisans and craftspeople who collaborated to create no fewer than 21 bespoke carpet designs, 19 curtain designs and 50 custom-made fabrics used throughout the hotel. 

That insistence on perfection is seen in each of the unique bedrooms, from the Anglo-Asian furniture inspired by Edward William Godwin’s work, the precise lines of panelling on walls and ceilings, soundproof leadlight windows, and the intricate patterns of floor mosaics. 

It is in the bedrooms that the flirty French DNA is most evident. At the press of a bedside button marked ‘Love’, the lights will automatically lower to a suitably erotic dimness, an appropriately mood-setting playlist will play at the press of the ‘Music’ button, and every room features black and white photography celebrating love, couples and romance. 

And in a very French nod to the excesses of love, in one of the Orient Express-inspired, brass-studded mahogany walk-in wardrobes, there is a one-way exit, knowingly called ‘The Mistress Door’ so that lovers can make a gracefully discreet retreat. 

On the sixth floor, is the hotel’s light-filled all-day restaurant. In a spectacular space, antiqued mirrors back ornately carved shelves that house a staggering number of ceramic vases, inspired by the ‘Peacock Room’, created in 1876 by local artists Thomas Jeckyll and James McNeill Whistler (the original is now housed in Washington’s Smithsonian Museum).  

The balcony offers views from Knightsbridge and Sloane Square to Battersea and the menu promises an array of perfectly simple French food. 

Accessed via a private entrance, the basement bar is the other place where that signature Parisian hedonism and decadence is at play. A moody colour palette of deep plum, terracotta, vanilla and black plays out across low banquettes and candle-lit tables. And there is a particularly enticing curtained-off dark corner, where we predict many secrets will be made to the sounds of the in-house DJ. Which is just as it should be. 

The hotel is open for reservations now. For more information, please visit atsloane.com 

…At Sloane

1 Sloane Gardens, SW1W 8EA; 020 3750 0750