Mrs Elisabeth GRIMBLE died on 2 March 1969, aged 82. It seems very likely that she was the (Baroness) Elizabeth (sic) VON VOLLMAR AUF VELTHEIM whose marriage to Harvey Neville Herbert GRIMBLE was registered in Q1 1924 in St Martin, London. When Harvey Grimble died on 25 October 1951, aged 65, probate was granted to "Arthur Barron accountant and Aribert von Vollmar barrister-at-law".
Aribert Weiner Heinrich Rudolf VON VOLLMAR AUF VELTHEIM was educated at Ampleforth, and his obituary, below, is from the Ampleforth Journal (see
http://www.ampleforthjournal.org/V_107.pdf):
"COUNT ARIBERT VON VOLLMAR
Aribert Heinrich Rudolf von Vollmar: born 9 February 1918 Berlin; Clifton College Preparatory School; St Oswald's House April 1932-July 1934; London University; Lincoln's Inn — called to the Bar; Army 1941 onwards in the war; worked as a barrister at the Munich War crimes trials; barrister; Civil Service; director of the Catholic Building Society; married Victoria Buxton 1955 (one son); died 3 April 2002.Aribert von Vollmar came of a German noble family, descended from a long line of German princes. Born in 1918 in Berlin, his father was killed within a few weeks of his birth at the end of the First World War. His mother then married an English army officer serving in India. In about 1924 or 1925 Aribert came to England and to Clifton College Preparatory School, and then in 1932 to Ampleforth.
After reading law at London University and then being called to the Bar at Lincoln's Inn, he served as a barrister until the war. In 1941 he joined the Army, training at Duncombe Park near Ampleforth, and joining the 79 Armoured Division/22nd Dragoons. At the end of the war he was ADC to the Duke of Grosvenor. He worked as a barrister at the Munich War Crimes trials (similar to the Nuremburg Trials). After working again as a barrister, he joined the Civil Service as a lawyer, and was eventually second in command of the Registrar of Friendly Societies. Later he was a Director of the Catholic Building Society. He had married Victoria Buxton in 1955, and they had one son, Rudolph 074). After retirement, he retired to the country, to Milcombe in Oxfordshire — where he became involved in local village life as craftsman, carpenter, painter, running the village fete, loved by all. At the age of 79 he began to read for a Mathematics degree at the Open University. He loved Bach. He was involved in hunting, especially with the Four Shire Basset Hounds. He was a lover of all country pursuits."
I suspect that the Duke to whom he was ADC was the Duke of Westminster (whose title and surname seem to have been confused here).