Michael Tsai:

James Tapsfield:

The extraordinary meltdown was caused by an Excel spreadsheet containing lab results reaching its maximum size, and failing to update. Some 15,841 cases between September 25 and October 2 were not uploaded to the government dashboard.

[…]

Alex Hern:

But while CSV files can be any size, Microsoft Excel files can only be 1,048,576 rows long – or, in older versions which PHE may have still been using, a mere 65,536.

While I don’t work with such massive files, I still prefer to keep CSV files in their original formats rather than converting them to Excel files. Likewise, text files stay as TXT plaintext files or, ideally, as Markdown text files.