I've just come off the phone to my cousin (today is her birthday). She is the clinical nursing manager ("Matron" in old money) in a large West Country hospital. She has spent her entire working life (>30 years) in nursing, much of it in A&E, operating theatres and Intensive Care. She knows a thing or two about PPE. She will not, under any circumstances, wear a face mask outside of her hospital. She has strongly advised her husband and two adult children against doing so. She has forbidden her youngest child (14) from doing so. Her reasoning is simple. She tells me that the risk of infection to the wearer from a poorly fitted face mask that is fiddled about with and constantly adjusted, removed and replaced exceeds, by a comfortable margin, the minimal mitigation of infection to others the same mask provides. She reminded me of one of the government's early advices - do not touch your face when you're out. Nobody, she believes, can avoid doing that when wearing a mask. Even she has trouble. In a hospital setting everything is controlled: surfaces, hand coverings, disinfection. In the supermarket or on a bus nothing is. She also explained that in most circumstances in hospital masks must be changed every 30 minutes. This is because it becomes a "sponge" absorbing everything that comes in and goes out, home to a nice warm, damp, microorganism ridden soup which will prosper in front of your nose and mouth.
Her advice is good enough for me and I will rely on it far more readily than some woolly jargon produced by a government scribe that tells me of the "emerging evidence" about the effectiveness of face masks. From tomorrow face masks and I part company permanently.