I also had ideas that it's from Wembley but quality of this bit is worser than on Wembley, it has tape flaws while Wembley is clear and excellent footage. It looks to be more closer to Knebworth footage quality.
It looks exactly like the clip, where Freddie is running from the left side of the stage holding his mic up at the beginning of the show, which comes from the DoRo footage of the first night, that's why I "THINK" it could be from the same source / night