That’s not how courts or laws work. Your repeated assertions that “the law does not say you require proof, so you do not require proof” have no merit or relevance.Afraid you are very wide of the mark - have you not read the legislation? Nowhere does it say tha any proof is required: the cause of the distress is wearing the mask, none other is specified as being required, When it started is irrelevant, because it's only applicable to the specific case in question, the effect is significant distress - no more is required by the law, so nothing further could be requested by the prosecution.
There is no way the CPS would take non-mask wearing to trial unless the defendant repeatedly claimed 'I am not except but I refuse to wear one' - the law is written in such a way that anyone claiming an exemption according to the specific reasons stated in the law has an exemption.
If someone is prosecuted for an offence, the prosecution is tasked with proving that the offence was committed, beyond reasonable doubt. Prosecutors the length of England can and do daily successfully prosecute offences. The proof on the testimony of witnesses, including defendants, can be used for this. Unlike Scotland, where corroborating evidence is required, in England it is common for cases to proceed on the evidence of a single witness.
Prosecuting lawyers regularly use questioning techniques to get defendants to admit things they might not want to admit. The case would not stop dead when the defendant says “wearing a face covering would cause me severe distress”. The prosecutor would then go on and ask, for example, “when did you realise that a face covering would cause you severe distress”, “have you tried wearing one”, “what happened then”, “can you tell me what specifically happens when you wear a face covering”, and so on, attempting to catch the defendant out or present inconsistencies in his or her story. The prosecutor would then invite the court to draw a conclusion.
Not to my knowledge, hence why I wrote my post in the conditional (“would”).I think that scenario is highly unlikely. Have any cases proceeded in this way?