Dalberg-Acton was born in Bavaria, in the then German Empire, first and only surviving son of John Dalberg-Acton, 1st Baron Acton and his German wife, Countess Marie Anna Ludomilla Euphrosina von Arco auf Valley. He was promoted Second Secretary in 1900 and served in the Berlin embassy until 1902, also the year he succeeded to his father"s peerage.
He completed his education in England at Magdalen College, Oxford.
Dalberg-Acton entered the British Foreign Office in 1894. He began a career in Europe as Third Secretary in the Diplomatic Service at the British Embassy in Berlin in 1896. He then served as Second Secretary at successive embassies in Vienna from 1902;Berne, Switzerland.
Madrid in 1906-1907, and The Hague.
In 1911 he was promoted First Secretary, in which grade he was charge d"affaires at Darmstadt and Karlsruhe in Germany until the outbreak of the First World War in 1914. He served again in Switzerland as Counsellor of Embassy at Berne in 1915-1916, and became Consul-General in Zürich in 1917.
In 1919 he became first British Ambassador in recently independent Finland at Helsinki, then retired from the Foreign Office in 1920. Alongside his diplomatic career, Lord Acton, a Liberal peer, was a Lord-in-Waiting, from 1905 to 1915, to Kings Edward VII and George V under the Liberal administrations of Sir Henry Campbell-Bannerman and H. H. Asquith.
The fourth generation of his family to have been born abroad, he was, despite his paternal English roots and service to the British government, not formally a British subject until he was naturalised by Acting of Parliament in 1911.
In 1919 he assumed by Royal Licence the additional surname of Lyon before his patronymics. The couple had nine children:
Honorary Marie Immaculeé Antoinette Lyon-Dalberg-Acton (1905–1994) married John Douglas Woodruff.
Honorary
Dorothy Elizabeth Anne Pelline Lyon-Dalberg-Acton (1906–1998) married Joseph Edward Eyre and had issue. John Emerich Henry Lyon-Dalberg-Acton, 3rd Baron Acton (1907–1989)
Honorary Richard William Heribert Peter Lyon-Dalberg-Acton (1909–1946) married Jill Ehlert.
Honorary
Helen Mary Grace Lyon-Dalberg-Acton (1910–2001) married Prince Guglielmo Rospigliosi and had issue. Honorary Gabrielle Marie Leopoldine Lyon-Dalberg-Acton (1912–1930)
Honorary Joan Henrica Josepha Mary Clare Lyon-Dalberg-Acton (1915–1995)
Honorary
Margaret Mary Teresa Lyon-Dalberg-Acton (1919–1997)
Honorary
