Marguerite de Beaumont (13 May 1899 – 30 July 1989) was a Girl Guide leader, horse breeder, author and poet.

She published biographies of Lord and Lady Baden-Powell, and was a recipient of the Silver Fish Award, Girl Guiding's highest adult honour.

[5] The dining room at the manor was converted into an emergency surgery, equipped at their own expense, to treat wartime casualties.

[5] In January 1945 the couple donated land to provide recreation facilities for returning World War II service personnel.

[6] de Beaumont died in Marlborough and was buried at St Michael and All Angels Church in Shalbourne, Berkshire.

Mason having pre-deceased her, de Beaumont left her entire fortune of £3 million, plus Shalbourne Manor, to her equine vet.

They make me feel very guilty at not having yet found time to devise a scheme of Scouting better adapted for them; but I hope to get an early opportunity of starting upon it.

[23] When the Jarman Centre – Cambridgeshire East's residential Girlguiding centre, named in honour of Marjory Jarman, opened in Newmarket in 1988, rooms were named in honour of de Beaumont, her sister and her mother in recognition of their early roles in local Guiding.

In 1948 she acquired the entire Wentworth stud of Welsh mountain ponies, including "the legendary" Coed Coch Glyndwr, together with many famous mares.

[31] She was "perhaps the most successful of modern breeders" of polo ponies, establishing a "dynasty" with the hack champion June XI.