The dazzling duo have been keenly followed by the media since they celebrated marriage of Tamara's younger sister Petra in a lavish ceremony, complete with a performance by the Royal Philharmonic Orchestra and £4,000 bottles of wine.
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On Monday, Tamara was the picture of elegance in a royal blue Victoria Beckham dress that fell just above the knee.
Former Armani model Slavica, however, opted for a sexier look in a black sequinned minidress.
And the fact that their family is in the spotlight didn’t seem to faze the two ladies, who flashed wide smiles for cameras.
While she's known for her lavish lifestyle, followed by viewers of her Channel 5 TV show Billion $$ Girl, Tamara is also committed to charity causes.
She's previously spoken of how her parents' humble beginnings have given her a sense of perspective about money.
The flamboyant heiress was hosting the party, which was also attended by Strictly star Holly Valance, the Duchess of York and Tamara Beckwith.
Afterwards, 27-year-old Tamara tweeted her followers: "Great night tonight in aid of Great Ormond Street. Thanks for all your support".
All the news as Duchess Kate's due date draws close...