The July 17 1923 edition of the Toronto Daily Star contained this photograph of a woman who some people thought was the most beautiful in England.
I could find nothing on M. V. Holt or Mrs. M. V. Holt – I have no idea who she was.
By the time of this photograph, Lady Diana Manners had become Lady Diana Cooper (1892-1986), as she had married Duff Cooper in 1919. The Coopers had been part of a set of intellectual aristocrats known as The Coterie; sadly, many of them were killed in the First World War. During the war, she apparently threw wild parties to try to escape the horrors of the war, and who can blame her?
In 1924, she played the Madonna in a revival of a play called The Miracle, and toured extensively with it for years. She also appeared in two early British colour films. YouTube has footage of Lady Cooper at a garden party in the 1920s, and an audio interview of her in 1969.