Mary Agnes Stourton Langdale was the second daughter of Arthur Joseph Langdale, a solicitor, and Catherine Agnes Eleanor de Bruynv who had married on 6 August 1872 in the Westminster district of London. Catherine had a son and daughter before Mary Agnes was born at 1, York Gate, Marylebone, on 2 December, 1877. Her parents took her for baptism to the Church of Our Lady, St. John's Wood, London six days later.

Little is known of Mary's early life, and it appears that the family spent a good deal of time travelling. Indeed both of Mary's younger sisters were born abroad; Gwendoline on Boulogne and Gertrude in Rome. This could well explain the difficulty on locating the family when the 1881 census return was made.

By the time the 1891 census was taken, thirteen year old Mary and her sister Gertrude were in Wimbledon, staying with a 62 year old widow named Catterina Jacomb. Their mother and father, along with two of their other children and four domestic servants, were in Tormoham, Newton Abbot. Towards the end of 1893 Mary's father died at the age of 55.

Though no record has been found of Mary, her mother and sisters in 1901 census records, we do know that Mary became a proficient pianist and played in many concerts in London.

Mary's younger brother Edward has been located in the 1901 census records, as a student in Kew. he went on to become a Civil Engineer and enlisted in the Royal engineers in WW1. Perhaps this had some bearing on Mary offering her services to the Red Cross; Edward disembarked in France in August 1916 and Mary was engaged by the Red Cross as a nurse the following month.

Mary was 38 when she joined the Red Cross, giving her address as 45 Church Road, Barnes. She served initially at Bulford Military Hospital and was transferred to Tidworth Military Hospital on 16 October 1916, a little over a week after her brother Edward had been killed in action.

It was whilst working at Tidworth that Mary became ill and died on 9 February 1917. She was buried in Tidworth Military Cemetery and her mother provided a Personal Permanent memorial for her, the inscription on the headstone reading: 'Pray for the repose of the soul of Mary Agnes Langdale V.A.D.'

She is also remembered on the Women of the Empire screen in York Minster.