Holding lande of the Crown by the service of rendering annually some small implement of war, as a bow, a sword, a lance, a flag, an arrow, and the like. Thus the Duke of Wellington holds his country seat at Strathfieldsaye and Apsley House, London, by presenting a flag annually to the Crown on the anniversary of the battle of Waterloo. The flag is hung in the guard-room of the state apartments of Windsor Castle till the next anniversary, when it becomes the perquisite of the officer of the guard. The Duke of Marlborough presents also a flag on the anniversary of the battle of Blenheim for his estate at Blenheim. This also in placed in the guard-room of $$$ Castle.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894