Agreed on all of these - all I was saying is that it was possible people were positive as they went into the stadium despite previous negative test. I agree its highly unlikely that Wembley itself was a large breeding ground for it.
The process was that you conducted the test at home, and it displays a result as 1 or 2 lines on the front (a bit like a pregnancy test, except without the pish). Each test has a QR code on it - you scan the QR code and enter your results online. NHS then send you an email/text showing you have taken a negative test. There's absolutely nothing to stop someone ripping open a test, scanning it & entering a negative result within 30 seconds - so again positive cases could have been transported into the stadium this way potentially.