Although 13 years older, Harriet was Queen Victoria's best friend. She was Mistress of the Robes and lived at grand Stafford House (now Lancaster House) near Buckingham Palace. When visiting Harriet's home, Victoria would say, "I've left my house to visit your palace."

Harriet's husband, the 2nd Duke of Sutherland, passed away in 1861. Queen Victoria was widowed later that same year. According to The Times, Harriet Sutherland 'was admitted by her Sovereign to a friendship so close and personal that on the death of the Prince Consort she was the one guest at Windsor Castle in whose company the Queen spent the first weeks of her sorrow and seclusion.'

Unlike most of the British aristocracy, Harriet favoured the Union during the American Civil War. The anti-slavery meetings she hosted caused her critics to refer to palatial Stafford House as 'Aunt Harriet's Cabin', a play on 'Uncle Tom's Cabin'.

Harriet only lived to age 62, passing in 1868. In 1871 one of her grandsons married Victoria's daughter, Princess Louise. In 1885 Queen Victoria stood godmother to Harriet's great-granddaughter, Victoria Elizabeth, daughter of the 4th Duke of Sutherland. She only lived to age two. Three of Harriet's descendants had the Queen as godmother and did not survive infancy. One wonders if Queen Victoria felt jinxed in this capacity.

In the story... Diana becomes chatelaine at Devonshire House in Piccadilly, London home of the 6th Duke of Devonshire, a bachelor. She has come to know the Duke because she grew up on the Chatsworth estate, the Duke's country seat. Devonshire House is a short walk from Stafford House, along the edge of Green Park. The 6th Duke is Harriet's uncle. Through this connection, Diana becomes an acquaintance of Harriet and of her best friend, Queen Victoria.