Political career
At the age of 21, at the insistence of his father, he reluctantly resigned his commission to stand as Liberal candidate for Midlothian (which was also known as Edinburghshire), where the Roseberys had long been prominent landowners. He was elected in the Liberal landslide in the 1906 election, one of almost 400 Liberals to be returned, and, at the age of 24, the youngest serving MP. He chose not to stand in the 1910 election, stating in a letter to his agent that his "politics are not far enough advanced to meet the views of the Liberal Party as at present constituted."
An obituary in The Times described him as a "dutiful rather than an enthusiastic participant in party politics", firmly resisting pressure to return to the House of Commons after the war.
Rosebery entered the House of Lords on the death of his father in 1929, taking his seat as the second Earl of Midlothian, a title bestowed on his father in 1911 but never used. He continued to be known as the Sixth Earl of Rosebery.
The same year he was appointed Lord Lieutenant of Midlothian, a post he held until 1964.
In 1938 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Hugh Macmillan, Baron Macmillan, Sir Thomas Henry Holland, James Pickering Kendall and James Watt.
In February 1941, during the Second World War, he was appointed Regional Commissioner for Civil Defence in Scotland. When the wartime coalition government broke up in 1945, Winston Churchill formed a caretaker administration to hold office until the 1945 general election. The new government was composed of members of the Conservative Party and the small groups which had allied with it in the National governments in office 1931–1940. Amongst these allies was the National Liberal Party to which Rosebery belonged.
One of the most unexpected appointments Churchill made was to install Rosebery as a member of the Privy Council and Secretary of State for Scotland. Both men had served together in the Liberal Parliamentary Party in the 1906–1910 Parliament. The caretaker Ministry was in office May to July 1945. So brief was his tenure at the Scottish Office that during the Royal Commission on Scottish Affairs (1952–4) he declined to give evidence on the grounds that he did not know what to say. Reputedly, his last words prior to his departing from the Scottish Office were "Well. I didn't make a bad job of this, did I? Didn't have the time".
