Our study analyses the way Wellington House structured its activity, means and methods used in building propaganda in the world. Wellington House was the secret department of British propaganda during World War I, with the mission to create a positive image of the British Empire in the world, and also to counteract the propagandistic actions of the Central Powers, especially of Germany. There is no Romanian study about the activity of Wellington House. Our study is based on an original document found in National Historical Central Archives in Bucharest. The document shows the unofficial methods of propaganda used by the British government during World War I and it is dated September 1916. It is a very consistent report (112 pages), written by Wellington House and is addressed to the Foreign Office. The complete title of the document is Third Report on the Work Conducted for the Government at Wellington House. In order to understand the propagandistic methods that Wellington House used, we took into account two examples: Italy and Romania. Those two countries, in the moment of writing the report, represented important strategic objectives for Great Britain and Entente and they were the object of some tough negotiations with the aim to make them take part into the war. The pages referring to Italy and Romania demonstrate the fact that Great Britain used very sharp official and unofficial propagandistic methods with a double aim: to annihilate the German influence and to create a favorable stream for the two countries to join Entente in the war. The propagandistic effort of Wellington House was more consistent for Italy than Romania; that shows the importance of the two states in Great Britain’s diplomacy between 1914 and 1916.