When I started watching this six hour documentary I certainly didn’t expect a ‘making of’ to make six hours of great TV. I also didn’t expect it to blow my mind.

I can honestly say that I kept talking about it to everyone I met for weeks afterwards. School gates, Tesco checkout, conference calls, I managed to talk about this to everyone.

If you haven’t already seen it the basic premise is that they have a deadline for when they will premier Frozen 2 for the first time – 12 months away – and they don’t know how the movie should end. They have a few ideas but they don’t know.

My first reaction to this was slight bemusement. How could you start making a movie if you didn’t know the ending?