NEW: Public Health England has found 15,841 positive cases that weren't registered on its data system

As a result, 22,961 have been reported today for England

The graph of cases now looks like this

What on earth happened? We still don't know. But *something* went wrong with the computer system on 24 September

This chart showing the build-up of missing cases was sent out to directors of public health in the north-west earlier today

The note sent to directors of public health explains what this means in practical terms.

They've been told:

1. This issue does not affect anyone's results. Everyone who tested positive was informed "in the normal way" and asked to self-isolate

2. The problem with the data had no impact on local lockdowns. The note says:

"This IT issue has no impact on the decisions that were made at GOLD this week regarding local restrictions; if anything it shows that the virus is in an endemic phase and rising."

The real impact is on Test and Trace. None of these positive cases have been contact traced - they're now dealing with an epic backlog

And that's actually an impact for everyone. 15k people untraced (and by now it's probably too late)... not good for containing the outbreak

Important to stress here: Public Health England might be sending out the emails, but this error goes back to Test and Trace. T&T sends the data, PHE reports it – and it never got sent by the Pillar 2 labs

I'm told a Serious Incident was declared yesterday. Serious is the word