Among the number of infected people posted everyday, the vast majority either experienced no symptoms

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The health secretary Matt Hancock and the schools minister Nick Gibb have been challenged on how reliable the “lateral flow tests” – which give results in around 30 minutes – really are.

On this morning’s BBC Breakfast, interviewer Naga Munchetty put it to Mr Gibb that the tests “detected just 48.9 per cent of Covid-19 infections in asymptomatic people”. The schools minister replied: “No, about a third have false negatives”.

There was a similar exchange in the House of Commons earlier in the week, when SNP MP Philippa Whitford confronted Mr Hancock with the results of a study that “revealed a sensitivity of just 48 per cent, meaning that over half of those with the virus would be falsely reassured they were negative”.

In his reply, the Health Secretary said “the lateral flow tests find around 70 per cent of those who are infectious” and that he would “urge” Dr Whitford – herself a former hospital consultant – “to go back, to study the details”.

But despite both ministers’ denials, the 48 per cent figure is supported by a SAGE paper dated 25 November. It compared the performance of the lateral flow tests used in the Liverpool mass-testing pilot with the “PCR” laboratory tests that have thus far formed the bulk of the UK’s testing programme.

So how did Mr Hancock arrive at the “70 per cent” figure (the mirror image of Mr Gibb’s “a third have false negatives” claim)?

They’re citing research by the government’s Porton Down lab and the University of Oxford dated 8 November. The teams found an “overall sensitivity of 76.8 per cent”, with over 95 per cent of people with high “viral loads” picked up by the test.

So how do we have such a wide range of results? The answer seems to be context. The Liverpool research was looking at real-world tests carried out “in the field” – while the Porton Down/Oxford figures come from several different settings.

The Porton Down/Oxford team found that the tests were most accurate when carried out by lab scientists (picking up 79 per cent of positive cases), slightly less so when done by trained healthcare workers (73 per cent) and significantly worse when carried out by “self-trained members of the public” (58 per cent).

The figures still look a little bit dodgy to me Omah, and I think they are massaged for effect.....