The striking twins, daughters of Diana's younger brother Charles Spencer, 9th Earl Spencer, and his first wife Victoria Lockwood, were perfectly coordinated on the night. But it was their choice of gowns that really got people talking.

Both sisters opted for off-the-shoulder black sheath dresses, but with different necklines and accessories. Amelia's gown featured a v-neckline and slim off-the-shoulder sleeves. She completed her look with a glittering diamond choker, matching diamond bracelet, diamond rings, and diamond drop earrings.

Her twin, meanwhile, wore a velvet gown with a straight neckline and off-the-shoulder sleeves. Eliza also accessorised with an array of diamonds - including a choker, identical bracelet, a diamond ring and diamond cuff earrings - and just like her sister, wore her blonde hair styled up in a sleek bun.

Royal fans were quick to point out similarities between the Spencer girls' gowns and the infamous 'revenge dress' worn by their late aunt, Princess Diana. Style icon Diana stepped out for a gala at the Serpentine Gallery in London in 1994 wearing a fitted, black, off-the-shoulder dress with an asymmetrical hemline and chiffon train that flowed behind her.