Guardian: I am standing on the wind-buffeted tip of the Strata tower, looking out through the blades of what appear to be an enormous propeller, at the London skyline and the green basin beyond. St Paul’s cathedral, across the river, seems close enough to touch. It’s the kind of view, and the kind of heroically stylised building, you would expect to see in some 1930s sci-fi movie: the perfect place for a hero and a villain to have a rooftop showdown. At 147 metres, the newly opened Strata is …