Sir Arthur James Balfour , 1st Earl of Balfour , KG , OM , PC ( 25 July 1848 â `` 19 March 1930 ) was a British Conservative statesman and Prime Minister of the United Kingdom from 1902 until 1905 . Arthur James Balfour , 1st Earl of Balfour , KG , OM , PC , DL ( 25 July 1848 -- 19 March 1930 ) was a British Conservative politician and statesman . He served as the Prime Minister of the United Kingdom from July 1902 to December 1905 , and as Leader of the Conservative Party from his appointment as Prime Minister to November 1911 .