How serious is the shortage of coronavirus tests? asks Robert Peston

I am being inundated with messages from people with what they fear may be Covid-19 symptoms who cannot work because they can’t get a test.

So what is going on? It is not all about the growing incidence of the virus. Though that is part of it.

Here is what a source from NHS Test and Trace tells me: "Demand for testing has gone through the roof. It’s almost like the loo roll phenomenon early on the year."

"We are doing more testing per head of population than other European countries but at current demand even once we have doubled that testing capacity (which we will do by end Oct) we will still have the problem you describe."

They added: "HMG has made a fundamental choice to test all care home staff once a week which uses a huge amount of our testing capacity but I think that’s right as that’s where the biggest risk is.

"We see a lot of people coming forward for testing who don’t have symptoms and just like every other bit of the NHS, if we don’t manage that demand there is a problem."

Or to put it another way, if you want a test you will have to be patient.

But as I said last week, this shortage of tests may lead schools and other institutions to shut temporarily if too many teachers and other staff are off work not really knowing if they are properly ill or not.

This testing shortage is a big problem.

PS - I understand that 100,000 tests are being delivered to social care settings every day.

So that is two-fifths of all testing capacity being absorbed to protect the elderly and vulnerable. Which most people would say makes sense.

But it means that with infections rising, there may well be inadequate capacity for the rest of the population for weeks and months, unless Boris Johnson's derided "moonshot" of exponential expansion based on new technologies actually works.