In the sixth of our in-depth eight-part series on the past, present and future of the corporation, Charlotte Higgins looks at how it became a news outlet that was trusted internationally but now faces fundamental questions about its purpose

• Part one: what the BBC’s origins can tell us about its future
• Part two: why is the BBC constantly criticised?
• Part three: how does the BBC deal with a crisis?
• Part four: the big beasts who shaped the BBC
• Part five: BBC there to inform, educate or entertain?