Forget the 90,000 pink cowboy hats and feather boas flooding into Wembley Stadium. While Harry Styles was whipping a generation of youngsters into a frenzy next door, supported by none other than Shania Twain, can you actually believe that? We, the rock rebels, the mums who still know every power chord from our mis-spent youth, were filing into the OVO Arena for a masterclass in unadulterated rock…