Mary Lalle Foley was born in Chertsey, Surrey, England on 9th October 1905. She was the youngest daughter of Lieutenant-Colonel Frank Wigram Foley and Eva Mary FitzHardinge Milman, 16th Baroness Berkeley.
Eva Mary Fizhardinge Foley was born as Eva Mary Fizhardinge Milman on 4th March 1875 in Colombo, Sri Lanka. Eva Mary was the daughter of Major-General Gustavus Hamilton Lockwood Milman and Louisa Mary Foley, 15th Baroness Berkeley. She died in Wycomb, Leicestershire on the 4th December 1964. The barony fell for the 2nd time into abeyance as there was no male heir and several female daughters.
The birth name Hon. Mary Lalle Foley was legally changed to The Honourable Mary Lalle Foley-Berkeley of Tyseley, Grimms Hill, Great Missenden in the county of Buckingham, Spinster enrolled in the Supreme Court of Judicature on 12th September 1951.
In contrary to male heirs, the barony title does not transfer automatically to the first born and it falls into abeyance if there are several sisters. All sisters can ask the crown for the title.
The abeyance of the barony title was terminated in favour to Mary Lalle Foley-Berkeley and she succeeded to the title of 17th Baroness Berkeley by writ suo jure on 5th April 1967.
She participated on several debates in the House of Lords between 1970 and 1977.
Mary Lalle Foley-Berkeley died unmarried and without children at the age of 87 in Wycomb, Leicestershire, England on 17th October 1992.
Mary Lalle Foley-Berkeley had a younger sister, Hon. Cynthia Ella Gueterbock, born as Cynthia Ella Foley on 31st January 1909 and died in December 1991 in Aylesbury, Buckinghamshire. Cynthia married Ernest Adolphus Leopold Gueterbock and had a son Anthony Fizhardinge Gueterbock, the current 18th Baron Berkeley after the death of his aunt, Mary Lalle Foley-Berkeley on 17th October 1992, 17th Baroness Berkeley.
GEC Peerage, Volume 2, pp. 118–149, Berkeley
Sanders, I.J. English Baronies, Oxford, 1960, p. 13, Berkeley
Smyth, John. The Lives of the Berkeleys, Lords of the Honour, Castle and Manor of Berkeley from 1066 to 1618, ed. Maclean, Sir John, 3 vols., Gloucester, 1883-1885 (First published c.1628) Vol 1, 1883 Vol 2, 1883 Vol.3, 1885