Which position was Lord Louis Mountbatten the last person to hold?

Admiral of the Fleet Louis Francis Albert Victor Nicholas Mountbatten, 1st Earl Mountbatten of Burma, KG, GCB, OM, GCSI, GCIE, GCVO, DSO, PC, FRS (born Prince Louis of Battenberg; 25 June 1900 – 27 August 1979), known informally as Lord Mountbatten, and to his family and friends as Dickie, was a British naval officer and statesman, an uncle of Prince Philip, Duke of Edinburgh, and second cousin once removed of Elizabeth II. During the Second World War, he was Supreme Allied Commander, South East Asia Command (1943–46).

He was the last Viceroy of India (1947) and the first Governor-General of the independent Dominion of India (1947–48), from which the modern Republic of India emerged in 1950.

The Governor-General of India (or, from 1858 to 1947, the Viceroy and Governor-General of India, commonly shortened to Viceroy of India) was originally the head of the British administration in India and, later, after Pakistani and Indian independence in 1947, the representative of the Indian monarch and head of state.

From 1954 until 1959 Mountbatten was First Sea Lord, a position that had been held by his father, Prince Louis of Battenberg, some forty years earlier. Thereafter he served as Chief of the Defence Staff until 1965, making him the longest serving professional head of the British Armed Forces to date.