In 1897, he was promoted to
lieutenant and served with a composite regiment of the
Household Cavalry in the
Second Boer War in
South Africa from 1899 to 1902. He was present at the
Relief of Kimberly and several other battles in the
Orange Free State, the
Transvaal Colony and the
Cape Colony. He was
Mentioned in dispatches, was awarded the
Queen's South Africa Medal with six clasps and was appointed a Companion of the
Distinguished Service Order (DSO) on 29 November 1900. In early 1901, the new King
Edward VII asked him to take part in a special diplomatic mission to announce the King's accession to the governments of
France,
Spain, and
Portugal. The following year, he was appointed a Member (fifth class) of the
Royal Victorian Order (MVO). In September 1902, Marjoribanks accompanied
Lord Roberts, Commander-in-Chief of the Forces, and
St John Brodrick, Secretary of State for War (and his father-in-law), on a visit to Germany to attend the German army maneuvers as a guest of
Emperor Wilhelm. He created a Knight 2nd class of the Prussian
Order of the Red Eagle during the visit. Marjoribanks and his wife attended the 1903
Delhi Durbar to mark the accession of King
Edward VII as Emperor of India. He was promoted to
captain in 1904, and from 1905 to 1908, he served as Military Secretary to the
High Commissioner in South Africa. In 1908, he was promoted to
major and was Director of Army Accounts and Quarter Master General for the
West Lancashire Division from 1908 to 1910. At the war's end, he served with the
Guards Machine Gun Regiment from 1918 to 1919. During the war, he was promoted to
lieutenant-colonel and created a Companion of the
Order of St Michael and St George (CMG). After succeeding as Lord Tweedmouth, he was
Lord-in-waiting to
King Edward VII and
King George V. He was said to be an excellent shot, having spent much time at his father's
Glen Affric Shooting Estate, and had an amiable personality, but had financial difficulties throughout his life. ==Personal life==