Speaking this week, chief medical advisor at the UKHSA, Professor Susan Hopkins, said evidence ‘was weak' that FFP3s were more protective than FRSMs.

Prof Hopkins said ‘if the evidence was strong that FFP3s really protected people from it, and we saw a definitive reductions in it, it would have been recommended'.

The medical advisor said wearing FFP3s for prolonged periods causing ‘significant harms', including ulcers and breathing and dehydration difficulties.

The inquiry was shown minutes from an IP (Infection Prevention) Cell meeting on 22 December 2020 in which Dr Colin Brown, who was then at Public Health England, saying: ‘Our understanding of aerosol transmission has changed. A precautionary approach to move to FFP3 masks [in all healthcare settings] whilst we are awaiting evidence should be advised.'

When asked about suggestions PHE was at the time pressing for the wider use of respirator masks, Prof Hopkins said it was a ‘really challenging time', adding: ‘The fact that PHE was giving and airing a different view is an example of not being involved in groupthink,' she said.

In January 2022. PPE guidance was updated to say FFP3s ‘must be worn' by staff treating patients with Covid.

The inquiry continues.