I believe that there was an increase in applicants, and applications, a few years when it became evident that there was a difference between the ways that many private schools and many state schools adapted to the Covid lockdowns. More children looking for private school places could have raised the level of selection.
In my corner of London, there was an increase in applications, though not necessarily distinct applicants,* *when the London Consortium went from having two different exams to having the same exam for all its schools, making it easier for a girl to apply to more schools. This might not have raised the level of selection.