Folkert van Wijk,
Most general histories of the 1880-1 campaign would include Lanyon's involvement.
Perhaps the best book on the subject would be Prof. John Laband's The Transvaal Rebellion: The First Boer War, 1880-1881.
Not theirs to save the day but where they stood, falling, to dye the earth
with brave men's blood for England's sake and duty...