In the medieval period, everyone in the upper percentages wanted a castle, and every castle had a dungeon: dark, dismal, cold, hopeless and rat-infested, or such is their filmic image. Dungeons were status symbols: everyone who was anyone had one. They had multiple uses: you could keep witches in them until it was time to burn them; you could shackle criminals in them, though it was often more economical to just hang them; and you could put rivals to the throne in them until you could fabricate enough evidence to proclaim them traitors and chop off their heads. And dungeons could be valuable wealth-creators, since holding foreign nobles for ransom could be lucrative. The trade was simple: you, the dungeon-possessor, got a lump sum of cash, and your prisoner got his freedom. In the reverse version, you paid a foreign dungeon-owner to sequester the political enemy of your choice.

And so it went, for hundreds of years, up to the modern age. In the 19th century, freedom and unfreedom began to assume their present-day forms. ‘Freedom’ had become reified by the 18th-century Enlightenment: it was what the embattled farmers of the American revolution were supposed to have been fighting for, though in practical terms they were fighting for the freedom of not paying taxes to Britain. The French revolutionaries started out with liberty, equality and fraternity, a noble ideal which included freedom from the aristocrats, though in the short term it ended in tears, thousands of severed heads and Napoleon.

But once Byron got hold of freedom, there was no turning back: freedom as an idea was here to stay. His The Prisoner of Chillon was romantic because he didn’t have freedom; that dubious character, Fletcher Christian, mutinied against Captain Bligh – in Byron’s version – as a gesture against tyranny and a bid for freedom. And Byron himself lost his life while fighting, more or less, for the Greeks in their attempt to regain their own political freedom. Not ‘Dieu et mon droit’ but ‘Freedom’ was engraved on the banner waved by many a 19th- and 20th-century revolutionary: slaves’ freedom from slavery in the American south, South Americans’ freedom from Spain, Russians’ freedom from the tsar, workers’ freedom from capitalist exploitation, women’s freedom from patriarchal systems in which they had the rights of children but the responsibilities of adults. And, eventually, freedom from Nazism and Iron Curtain Communism.

Freedom to write, freedom to publish, freedom of speech: all are still being fought for in many countries in the world. Their martyrs are numerous.