Here is the full report that a PP mentioned, where Dr Colin Axon gives his views on cloth face masks. He comes at it from an engineering point of view, rather than medical.
*"Standard face coverings are just "comfort blankets" that do little to reduce the spread of Covid particles, a scientist advising Sage on ventilation has said.
Dr Colin Axon, who has advised the government on minimising the risk of cross-infection in supermarkets, accused medics of presenting a "cartoonish" view of how how tiny particles travel through the air.
He warned some cloth masks have gaps which are invisible to the naked eye, but are 500,000 times the size of viral Covid particles.
"The small sizes are not easily understood but an imperfect analogy would be to imagine marbles fired at builders' scaffolding, some might hit a pole and rebound, but obviously most will fly through," he told The Telegraph.
The mask debate has been reignited this week after the Government published 'Freedom Day' guidance recommending their continued use. It led to Sadiq Khan, the Mayor of London, enforcing their continued use on the London Underground.
Dr Axon said the public need to be offered a wider view of the science behind face masks, rather than the "partial view" of information being pushed by medics over their effectiveness.
'Medics have a cartoonish view of how the world is'
"Medics have this cartoonised view of how particles move through the air - it's not their fault, it's not their domain - they've got a cartoonish view of how the world is," he said.
"Once a particle is not on a biological surface it is no longer a biomedical issue, it is simply about physics. The public has only a partial view of the story if information only comes from one type of source. Medics have some of the answers but not a whole view."
Dr Axon, Brunel University's senior lecturer in engineering, said that the true mechanisms involved are best evaluated through science.
"When the particle enters another body it returns to a biomedical issue but the mask debate is about the particle journey," he said.
"Masks can catch droplets and sputum from a cough but what is important is that SARS CoV-2 is predominantly distributed by tiny aerosols."
Dr Axon said that medics were "unable to comprehend" the miniscule elements at play, adding: "A Covid viral particle is around 100 nanometres, material gaps in blue surgical masks are up to 1,000 times that size, cloth mask gaps can be 500,000 times the size."
Dr Axon, whose report on ventilation in supermarkets was used by both Nervtag and Sage to aid decisions, says that medics "cannot have it both ways" over asymptomatic spread.
He added: "Not everyone carrying Covid is coughing, but they are still breathing, those aerosols escape masks and will render the mask ineffective."
Droplets from coughs are much larger, and more likely to be stopped by a properly used mask, Dr Axon says. An Oxford study last summer concluded that masks were "effective" in reducing the spread of the virus.
'We are entrenching bad behaviour'
However, other studies have cast doubt on their effectiveness. A subsequent Danish study involving 6,000 people concluded that there was no statistical difference in infection spread in non-wearers, while data on US states with non-mandated usage failed to show a correlated uptick in cases.
"The public were demanding something must be done, they got masks, it is just a comfort blanket," Dr Axon noted. "But now it is entrenched, and we are entrenching bad behaviour.
"All around the world you can look at mask mandates and superimpose on infection rates, you cannot see that mask mandates made any effect whatsoever.
"The best thing you can say about any mask is that any positive effect they do have is too small to be measured."*