Anything Goes : Dunkirk's 7 minute trailer is outrageous. How long should trailers be and what should they show? by Richard Fitzwilliams

I am much looking forward to seeing and reviewing Christopher Nolan's Dunkirk for several outlets but will avoid its 7 minute trailer as I try to avoid all trailers. What on earth is the point of seeing clips out of so many parts of the film before you see it? Trailers often contain spoilers. If you see a James Bond trailer or one for an epic you find they cannot resist spoiling the surprise that is the magic of cinema by showing extracts from all the spectacular scenes. They are a necessary evil as they create buzz and advertise a product but 7 minutes, this is surely crazy!!