There is something wonderful about watching a great actor in action and Kathryn Hunter is one of the best. In The Emperor she stands on a virtually bare stage and in swift, almost seamless motion, brings a whole world to life. The world is that of the Emperor Haile Selassie of Ethiopia, as conjured by the words of his servants which were recorded by the Polish journalist Ryszard Kapuściński and have been adapted for theatre by Colin Teevan. The play is directed by Walter Meierjohann, thus reuniting the writer, director, actor team that last worked together on Kafka's Monkey.

Like that piece, this is a tour de force of theatrical story-telling. With the simplest of props – a stick, a hat, a jacket unbuttoned or closed – Hunter embodies a range of characters, from the loyal valet, to the camp master of ceremonies, to a timid door opener, to the minister of information so devoted to his master that even the death of his own son cannot shake his faith.

The words recorded and delivered are extraordinary in their force of detail. They recount how a man, "King of Kings of Ethiopia and Elect of God" slowly lost control of his own kingdom, a land where a servant followed him around with cushions so that his feet were never left dangling from a throne, where his people bowed before him as he walked amongst them, where he controlled every aspect of their lives.

It asks questions about the way power corrupts and warps not only an absolute ruler, but also those around him – and makes a distinction between "development" which builds an infrastructure and the welfare of a people. It was unrest among students and neglect of the poor in a famine that brought Haile Selassie down, and we briefly see Jonathan Dimbleby's famous film which exposed the suffering.

But otherwise it is Hunter we rely on, alone save for the musician Temesgen Zeleke, providing music, a sung commentary and – briefly – incarnating the lost, rebellious son. They sit quietly together at start and end, before Hunter begins her acts of evocation, suggesting with small shifts of voice and gesture not only the character of the speakers but also the events they are describing, and the stance and influence of the man they believed was a God.

She has a stand-up comedian's timing, and sense of the presence of her audience; she rounds each anecdote with graceful precision, her hands carving shapes in the air, making you see the bird of paradise that the words describe, or the puffed up officials who have received promotion. Her ability to find and communicate feeling is astonishing. Tears suddenly spring into the Minister of Information's eyes as he matter-of-factly describes his son's arrest and death; just as quickly they are wiped away.

When the Emperor's clerk is sacked in one of the palace purges, Hunter makes him shrivel in front of you. "I was sent home for ever. I no longer existed." And the final scenes, when the palace is dark, and the rain falls and only the valet is left to serve a man who once ruled all he surveyed, echo with a sense of history. It is a richly absorbing hour.

The Emperor is at the Young Vic until September 24; Home, Manchester from Sept 28-Oct 8; Les Théâtres de la Ville, Luxembourg Oct 12-14