[1] She had two older siblings, William Burns, who died young, and American-born British art collector Walter Spencer Morgan Burns (lord of the Manor of North Mymms, who in 1907 married Ruth Evelyn Cavendish-Bentinck,[2] a daughter of William and Elizabeth (née Livingston) Cavendish-Bentinck).

"[7] Mary, Viscountess Harcourt, was appointed a Lady of Grace of the Order of St John and then Dame Grand Cross of the Order of the British Empire (GBE) in 1918,[5] as well as the silver medal of the American Red Cross and the Belgian Médaille de la Reine-Élisabeth After her husband's death in 1922, she became chairman of the council of the Society for the Overseas Settlement of British Women in 1927.

Lewis, whose nickname was "Loulou", was the only surviving son of politician Sir William Vernon Harcourt (former Home Secretary and Chancellor of the Exchequer) and his first wife, Theresa (née Villiers) Lister Harcourt (sister of George Villiers, 4th Earl of Clarendon).

[14] He had taken an overdose of a sleeping draught, and there were rumours of suicide following accusations of sexual impropriety by Edward James, a young Etonian who later became an important collector of surrealist and other contemporary art.

James's mother spread the story in society although the accusations remained unknown by the wider public for fifty years.