The 32-year-old daughter of the Marquess of Milford Haven, the first cousin of the late Prince Philip was photographed as she got out of her wedding car arriving at the venue. In keeping with tradition, Lady Tatiana wore a face veil as she entered the cathedral.
She chose a white, full-length bridal gown with cap sleeves paired with a sash.
Images from the day show one of Prince Harry’s ex-girlfriends Cressida Bonas making her way to the ceremony.
In January, Lady Tatiana revealed that Mr Dru had proposed while the couple were on a skiing holiday in the Alps.
Lady Tatiana, a distant cousin of the Queen, got engaged to entrepreneur Mr Dru in the Swiss resort of Verbier.
Her royal friends, Princesses Beatrice and Eugenie, were also on hand to celebrate.
Lady Tatiana’s close friend Violet Manners, daughter of the Duke and Duchess of Rutland who was on holiday in Verbier at the same time, also shared her well-wishes on social media.
She wrote: “Yes yes yes yes yes! So happy I got to see you both glowing this week. Big love xxxx.”
When Lady Tatiana posted about the engagement on Instagram, Ms Bonas was among those who congratulated the couple on the news of their engagement, writing: “Beauties.”
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She is an equestrian who trained under Olympian Charlotte Dujardin.
Lady Tatiana was educated at the elite £12,000-a year Millfield private school in Street, Somerset.
She once wanted to be a ski instructor but now works training dressage horses.
Mr Dru studied History at Oxford before founding Tripr, a social travel app.
He also founded Spires Tutoring before moving into the world of startups.