Now I can understand that you might have the intention to be clear, but since you aint for me, a few questions to see if we can make that happen anyway:
What is C4?
In what country are you, as that most probably is the country in which we can recieve this channel?
What time will it be broadcasted? What time-zone is that, so the rest of the world can calculate what time that would be for them?
What is the documentary called, so those who dont have C4 and are still interested can give google / youtube a shot.
Basicly:
Just imagine yourself being on the other side of the world then you currently are and trying to understand your post without inside info .