Members of the extremist Quebracho movement charged the compound in the Argentine capital after smashing through a protective barrier.
Riot officers forced them back before some demonstrators launched missiles and flares at police, who returned fire with rubber bullets, water cannon and tear gas.
In the minutes prior to the attack, extremists had set fire to a Union Jack flag and an effigy of Prince William, the Duke of Cambridge.
Speaking to Sky News Online, Quebracho leader Fernando Esteche, said: "The burning of the flag and effigy symbolised our disgust at this British invasion of our national territory. Read More