Sorry
@ContinShots, whilst I agree with you it is sensible to secure S2 cartridges, maybe you can post a link to the law section that you are referring to?
I have already pointed a link to the Firearms Security Handbook, so I would be grateful for you pointing out something that contradicts that. Any regular visitor to SD will be only too aware of FEOs & FLDs, all over the country, adding/embellishing extra conditions onto the various acts of parliament, as well as re-interpreting the statutory guidance from the Home Office, and I think it is only right to be aware of the various bits to be able to question those interpretations.
Saying, "I know I don't have to look up the S2 stuff, but I choose to do so" can only be seen by the FEO as being responsible & informed. A competitive clay shooter, buying a pallet load of cartridges at the start of a season, may choose to store them away from the cabinets, and shouldn't be penalised if they are complying with the law.
As for a S21 prohibited person, they sh/would know the restrictions on themselves from the release papers, even to the point that they must not be in possession of airgun pellets as well as S2 cartridges. So, they should be smart enough not to pick anything up that they shouldn't , and even refuse being handed something. That is their responsibility as an adult, as well as a S21 Prohibited Person, rather than mine. I keep shooting related items out of sight of casual visitors such as tradespeople, but they shouldn't be picking up something unrelated to their task anyways.