At the risk of swimming against the tide, here - is this really a film at all? Certainly it's an exceptionally high-spec production of a concert from Billie Eilish, and it clearly demonstrates that she is charismatic, engaging and talented - but we have seen so many films of concerts that perhaps aren't in 3D, but that do, and have done, exactly the same as this for decades. Britain's largest indoor venue is packed to the rafters with adoring - even adulatory - fans from a myriad of backgrounds, sexualities, races, creeds and many of them believe that Eilish is their best friend; their…