Covid: Test error 'should never have happened' - Hancock

The technical error was caused by some Microsoft Excel data files exceeding the maximum size after they were sent from NHS Test and Trace to Public Health England.

The BBC has confirmed the missing Covid-19 test data was caused by the ill-thought-out use of Microsoft's Excel software. Furthermore, PHE was to blame, rather than a third-party contractor.

The problem is that the PHE developers picked an old file format to do this - known as XLS.

As a consequence, each template could handle only about 65,000 rows of data rather than the one million-plus rows that Excel is actually capable of.