How to explain an increasing proportion of people testing positive for COVID if there is neither an increase in proportion of genuine cases nor increase in the false positive rate

 A few people have argued (see e.g. here and here) that, despite the official Government statistics, real COVID cases are not increasing and that most COVID positive test results are false positives. The obviously strong argument against this is the evidence that the proportion of positive tests is increasing as shown here:

Ignoring the possibility that …