For a start is has stable doors and will not be classed as a shelter - but as a pony barn.?
Just dont ask first - do it.
Have to say after working my way through 1500+ enforcement notice appeals, its a bag of nails.
Anyone that has a field shelter would be advised to move it at least every 10 months and take dated photos and videos.
Seen a couple of appeals where mobile shelters have been classed as buildings.
One stood out, was big mobile shelter on metal skids with towing eyes -20 foot x 12 guy had photos even video of it being moved.
But council had evidence that it had not been moved in a year , so planning inspector classed it as a building that needed planning permission.
Even said it was anchord to the floor with its own weight

Some councils are ruthless and some inspectors differ on opinions