I’m up so watching the US stuff so might as well say that there were three pilots of lamp tests, as I understand it: two were 90% or so, but the GM pilot came out at 43%. Govt doesn’t like the GM result so have basically told them to do it again. But https://twitter.com/DHSCgovuk/status/1324432641685413888

GM pilot people think the way they’ve tested the test, as it were, is much more aligned to the way actual humans would use it, ie not under really specific lab conditions - early in the morning before they’ve brushed their teeth or whatever - and stand by it.

So in conclusion: as the Guardian says, the test was less than 50% sensitivity in a pilot. (The figures I have are 43%; the letter has it at 47% - not sure why, but either way less than half). It might not happen to be the pilot that the government likes, but it’s still true.