This documentary oversimplifies the fatal switch in German strategy from targeting RAF fighter resources to their terror attacks on London. They make it seem a considered, strategic decision, but that's not what it was at all. It was an ego-driven act of revenge.
It started with a German bombing raid that got lost and opted to jettison their bombs over what turned out to be a part of London, despite existing orders that the British capital was not to be attacked without specific orders from Hitler. This understandably angered Britain, who retaliated with a bomber strike on Berlin. Faced with the humiliation of the bombing of Berlin, the decision was made to switch the target to London. NONE of this important linkage was included in the production, though it could've been covered in less than 60 seconds. That's just lazy!