Video report by ITV News Health Editor Tom Clarke
A local lockdown of Leicester is seen by most experts as the right and necessary response by the government. The scale of the outbreak in the community there needs to be contained to prevent coronavirus spreading more widely.
But why did it come to this?
On Tuesday we learned it was Ivan Browne, the Director of Public Health in Leicester, that first contacted Public Health England (PHE) on June 9 to report what looked like an increase in his local cases.
This wasn't an outbreak that was first picked up by the national test and trace system.
A full six days later PHE replied to him agreeing something was going on. And the same day - June 15 - more testing capacity was sent to the city. Two days later health secretary Matt Hancock announced in Westminster there was an outbreak in the city.
Based on the data available to Leicester, it had no idea "outbreak" was the way to describe it.
It wasn't until Friday 26 June that the council finally got hold of data informing them where the people testing positive for coronavirus actually lived.
The data it needed to bring an outbreak under control.
It was only four days later, the city was shown the results of a PHE investigation into their outbreak and ordered into an extended lockdown.
"The government has totally lost its grip on the data" is how one leading public health expert described the situation that led to the Leicester lockdown - and what fate might await other towns and cities up and down England.
To any interested observer, there was no early indication that Leicester had a problem.
The data available to the council, to independent scientists, and even members of the government's SAGE committee is dominated by what's called "pillar one" tests. That's those carried out by NHS and PHE labs covering cases in hospitals, care homes and care workers.
According to that data there are clear hotspots around the country.
Higher than average rates of infection can be seen Bedford, Ashford, parts of Manchester and Sheffield. But what did that data tell us about Leicester? Nothing.
This graph shows the pillar one data for Leicester. It shows cases declining since the peak of the initial outbreak as they have done across much of the country.
The total number of lab confirmed Covid-19 cases for Leicester is 1,056 according to this pillar one data. Hardly an outbreak. So what was missing?
Well to answer that you have to look at the other coronavirus testing data included in "pillar two". These are the tests from drive-through testing labs, and home testing kits that form the basis of the government's community testing programme and "test and trace" system.
This data is collected by the commercial labs and partners running the system.
Once the council got hold of pillar two data - just four days ago - it became aware that instead of 1,056 cases there had in fact been 3,216. More than a three-fold increase.
And it's not just a lack of testing data. It's the information that comes with it.
What we now know is that until very recently there was no geographical information associated with any of the 4,750,954 tests reported to have been carried out under the pillar two system. None.
So no-one outside the system itself can have any access to where any individual may have tested positive. One of the most basic pieces of information needed if you are trying to control an outbreak.
Councils now receive a weekly update on data from pillar two tests - but it only recently includes postcode level data. Daily data - including addresses, ethnicity, occupation which are needed to contain an outbreak - is still not available.
It's no wonder Leicester had no idea how bad its outbreak was becoming.
But it raises very grave questions about how the national test and trace system is supposed to spot and control outbreaks elsewhere.
The system is supposed to detect outbreaks as they occur and trace any contacts to prevent them getting worse. It's clear from the fact that Leicester finds itself being locked down 20 days after it first alerted PHE to a problem that the system has failed to work.
Where does that leave other towns and cities up and down England which - as things currently stand - can't tell whether they are experience an outbreak or not? And if they are, what confidence can they have in the system supposedly designed to stop it?
Coronavirus: Everything you need to know