"Distress while wearing a mask"

I accompanied my husband to an outpatients appointment. On passing through the main entrance a hospital employee, who was apparently checking that everyone attending the hospital was wearing a mask, asked if I was happy to wear a mask (my husband already had one on) I replied that it would cause me great distress (I have PTSD and depression and anxiety and panic attacks).  The response was friendly and cordial and I proceeded, unmasked, to the outpatients' reception area. 

Here was a different story.  The receptionist told me that I must leave the building as I was not wearing a mask.  My husband explained my problem with wearing one, I was asked to see my GP's letter confirming this and to see my exemption card.  My husband (I was struggling to maintain steady breathing and remain calm and NOT have a panic attack by this time) told her what he had told the chap at the main entrance.  The staff member laughed at the suggestion that the psychological issues I have would prevent me from wearing a mask then turned away to the computer, muttering and snorting with laughter. 

I left the hospital shaking and in tears.  I know I know, and I am trying, despite the dismissive and flippant responses will inevitably come to the minds of some reading this but, I should point out that there is NO requirement, in law, for anyone who is exempt from mask-wearing to provide ANY written evidence of this. The GOV.UK website advice states that people should not routinely be asked to provide written evidence, and that doing so is a choice and not necessary in law.