I'm not sure that putting a container down on ground would class as development, it most certainly isnt operational developmentYes - I've just asked about installing a container in a field in green belt for secure machinery & tool storage and received a reply from my planning authority (Warwick District), which says:
A quick glance through the permitted development legislation indicates that this would need an application for planning permission...An application would be assessed in terms of green belt policy and landscape impact, visual impact, for example. I would expect a shipping container to be found unacceptable on the basis that it is not an appropriate form of development. While providing security it would impact on the quality of the environment.
"inappropriate development in the green belt" - so we can't have one here.