The 32-year-old daughter of the marquis of Milford Haven, the late Prince Philip’s first cousin was photographed as she stepped out of her wedding car and arrived at the venue. In keeping with tradition, Lady Tatiana wore a face veil when she entered the cathedral.
She chose a white, long wedding dress with cap sleeves and a sash.
Images of the day show how Cressida Bonas, an ex-girlfriend of Prince Harry, attends 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, became engaged to entrepreneur Mr. Dru in the Swiss seaside town 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 vacationing in Verbier at the same time, also shared her well wishes on social media.
She wrote: “Yes yes yes yes yes! So glad to see you both glowing this week. Big love xxx.”
When Lady Tatiana posted about the engagement on Instagram, Ms Bonas was among those to congratulate the couple on the news of their engagement, writing, “Beauties”.
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She is a rider 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 become a ski instructor, but now she is working on training dressage horses.
Mr Dru studied history at Oxford before founding Tripr, a social travel app.
He also founded Spiers Tutoring before entering the world of startups.