Loading/Strapping Question (UK Question)

This may seem an obvious answer but would appreciate a sensible answer. I am looking for an answer thats relevent to UK law as that is where I am based.

If I was to drive a Class 2 vehicle that is curtain sided and had any of the combination of the following load:-

- 5 pallets only
- 6 pallets only
- full load of pallets
- pallets that have ADR

The question is do you strap the pallets down or do you trust that the curtain is strong enough to hold the goods inside?

I have asked for it to be strapped and supervisor said its not necessary, plus the fact they do not really supply internal straps anyway.

Should all pallets inside be strapped up or can they be left loose for the curtain to hold them?, but what about if your on an orange plate should all load be strapped or loose?

The pallets themself are loaded with goods and then wrapped in clear plastic