Mark Ravenhill meets Keith Johnstone, the world's most celebrated improvisation teacher
For the last 20 years, I've always been in charge: I've given acting classes, led playwriting workshops, directed dramas. Never in my adult life have I sat in a classroom and waited for a teacher. But now I'm sitting in a London church hall, waiting. I've signed up for a week-long course with the world's most celebrated improvisation teacher, Keith Johnstone. I suddenly feel nervous.Much of Johnstone's method was dev…