I found this an informative 25 minute programme on what have been the different problems with the English test-and-trace system. I knew snippets but this pulled it together for me. They are finally making changes but so many weeks wasted and there are still problems.
www.theguardian.com/news/audio/2020/aug/20/the-trouble-with-englands-test-and-trace-system-podcast?CMP=Share_iOSApp_Other