Test, track, and trace.
https://fullfact.org/health/NHS-test-and-trace-app-37-billio...
"The NAO said that of the approximately £13.5 billion spent on the NHS Test and Trace programme in 2020/21, £35 million was spent on the app.
The vast majority of the spending in that year was accounted for by testing (£10.4 billion)."