Date night! Princess Beatrice looks elegant in a black dress as she and her husband Edoardo Mapelli Mozzi attend the opening of the new luxury hotel The OWO

Princess Beatrice looked chic in a black blazer last night as she enjoyed a date night with her husband Edoardo Mapelli Mozzi.

The 35-year-old daughter of the Duke of York beamed as she joined Edo and a host of other celebrities for the opening of The OWO in Whitehall yesterday.

Built on the historic royal site of Whitehall Palace, Britain’s Old War Office has undergone a monumental six-year transformation to become a hotel, as well as a selection of restaurants, bars and even a spa.

The couple appeared in good spirits last night as they attended the event and posed for photos alongside TV personality Tamara Beckwith and Giorgio Veroni.

Mother-of-two Beatrice opted for an elegant blue patterned dress for the occasion, which she teamed with a black blazer and stylish stiletto heels.

The Duke of York’s daughter beamed as she joined Edo and a host of other celebrities for the opening of The OWO in Whitehall yesterday

Indian billionaires, the Hinduja brothers, formally bought the 580,000 square meter site in March 2016 for more than £350 million.

The Hindujas, who are ranked as Britain’s richest businessmen with a £12 billion steel fortune, teamed up with Spanish group Obrascon Huarte Lain Desarrollos to buy a 250-year lease on the historic property.

Built in 1906 and bombed eight times during the Blitz, the seven-storey building has a thousand rooms and two and a half kilometers of corridors.

The Old War Office hotel, which opened last night, has seven floors below ground and seven floors above.

There will be 120 bedrooms, nine restaurants – one of which is on the roof – three bars, while the pool, spa, gym and ballroom will all be underground.

Prospective hotel guests enter from Whitehall (although VIPs are also wheeled into the courtyard) and step into the Grand Hall, where they are greeted by the imposing Brescia marble staircase with richly veined alabaster balusters.

The staircase, of which Princess Beatrice and Edo took a number of photos, was William Young’s great tour de force.

It was described by TE Lawrence, who worked in the Geographical Department of the War Office in 1914, as so opulent that it was ‘intended for the use of field marshals and charwomen only’.

More recently, the building featured in four James Bond films – Octopussy, A View to a Kill, License to Kill and Skyfall – portrayed as the MI6 headquarters, where M’s office was located.

Princess Beatrice’s night out comes after the couple celebrated their daughter Sienna’s second birthday by sharing a rare look at the young royal.

The couple appeared in good spirits as they attended the event last night – posing for photos alongside TV personality Tamara Beckwith and Giorgio Veroni

Sienna, whose mother is Princess Beatrice, looks cool and stylish despite being just two years old in a photo shared by her property developer father on Instagram.

She is dressed in a long-sleeved gown with red floral print and wears a Mexican sombrero as she walks barefoot on a path covered in soft material.

Sharing the photo with his Instagram followers last week, the 39-year-old wrote: ‘Harry birthday baby girl. You bring us so much love and joy every day.”

Sienna’s adorable photo is a rare glimpse into the young royal’s life, with her parents choosing to keep her private.

Royal fans first saw Sienna earlier this year when her aunt, Princess Eugenie, posted a photo on Instagram of the toddler with her cousin August (Eugenie’s eldest son) as they appeared mesmerized by the penguin enclosure at London Zoo.

Edo’s sweet tribute to his daughter comes days after a new post dedicated to his wife Princeaa Beatrice, following their loved-up performance at Vogue World in central London last week.

He shared photos from the event on social media and wrote: “My beautiful wife. It brings joy to my life.”

Mother-of-two Beatrice opted for an elegant blue patterned dress for the occasion, which she teamed with a black blazer and stylish stiletto heels

At the exclusive London Fashion Week event, the royal couple were joined by Beatrice’s sister, Princess Eugenie, who stunned in a teal dress as she made her first public appearance after the birth of her son Ernest in late May.

Eugenie shared a photo of the sisters – the daughters of Prince Andrew and Sarah, Duchess of York – on their way to the event: ‘It was so lovely to attend Vogue World: London this week. The event celebrated Britain’s rich cultural scene.

“The arts are under threat in Britain and Vogue World will be a timely reminder of how important they are, how important a part of our lives they are and how much they need our support,” wrote Anna Wintour. .

Next to it was a photo of the sister in the back of the car on the way to the event – Britain’s answer to the Met Gala.

Mother-of-one Beatrice wore a black floral dress as she attended the Vogue World event at the Theater Royal, Drury Lane in central London with Edo, who looked dapper in a white tuxedo jacket and black trousers.

As they posed for photos, Edo kissed his wife, who in turn couldn’t help but giggle sweetly during her husband’s PDA.

The couple both seemed thrilled to be at the event together as they were photographed beaming as they had their photos taken.

Prince Andrew and Sarah Ferguson’s daughters Beatrice and Eugenie appeared to have left their children at home as they enjoyed their evening in the West End.