This is why cases in university towns have changed significantly today.

Commercial DHSC Test & Trace appear to have been using addresses from NHS records.

Many students that moved to university had not yet registered with a GP. https://www.gov.uk/government/publications/covid-19-geographical-allocation-of-positive-cases/geographical-allocation-of-positive-covid-19-cases

"Until the end of August, approximately 4% of positive laboratory-confirmed coronavirus cases had given an address at point of testing that was in a different local authority compared to the permanent address registered on the NHS database (Summary Care Record)."

"Between 1 September and 12 October, Public Health England (PHE) analysis found this had risen to 12% of cases, driven mostly by younger people aged 17 to 21, consistent with the relocation of many students across the UK."

It is unfortunate that PHE are making this statement as opposed to NHS Test and Trace or DHSC (who is responsible), as the error appears to have been with the methodology employed by commercial DHSC Test & Trace.

See e.g. this story from 12 October discussing students from the London Borough of Richmond (at universities outside the borough). https://www.standard.co.uk/news/health/positive-student-coronavirus-tests-home-address-computer-glitch-a4568656.html

It would appear that, up until yesterday:

- local authorities with high numbers of progression of school leavers to university (e.g. London Borough of Richmond) would have had their cases overstated

- university cities and towns would have had their cases understated.