//I really don't want Johnson making decisions based on the views of know-nothings such as one finds here.//
One thing is for sure - the decision to mandate face coverings was certainly made as a result of pressure from the Twitterati. At the beginning of the pandemic the WHO was quite clear that the widespread wearing of non-medical grade facemasks by the wider population was of little benefit in preventing virus spread. If you look at this paper (NERVTAG paper: face mask use in the community) from 13/4/20:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/890043/S0127-nervtag-face-mask-use-in-the-community-130420-sage25.pdf
Under "options" on p2 you will find this:
Policy Option:
Universal face masks in the community.
Pros:
Given possibility of significant presymptomatic transmission, may
provide a very small incremental increase in protection.
Cons:
Evidence of lack of effectiveness. May result in decreased compliance with social distancing, hand hygiene etc. Unlikely to have a significant impact whilst social distancing in force.
Supply issues.
Level of support:
Not recommended.
Similar non-recommendations were made by the WHO (you can look them up). The WHO went further and suggested that the risk of self-contamination by people untrained and undisciplined in the use of PPE (something I have touched on many times) far outweighed any small benefits that may be evident.
But lo and behold, less than two months later, following a widespread campaign on social media accusing no mask wearers of being "granny killers" the advice was reversed and face coverings - with all their drawbacks still evident but not emphasised - were mandated.
So be careful what you wish for when you ask politicians to steer clear of unqualified loud-mouths.