The blue-and-purple hoop is supposedly there to answer questions that arise in chats, but it’s a slippery slope from providing bus times to annihilating the human race, writes Polly Hudson
As the star teams up with director Michael Grandage for his first West End part in 17 years, the pair discuss the thrill of putting on a new play, how it updates Ibsen for our times – and a Trainspotting-esque toilet encounter in Russia