Do the police bother to give a detailed explanation to go with tweets like that, of what was specifically wrong rather than a vague statement.
My guesses are:
Van only appears to be secured by straps on the front wheels
Insecure loader due to the use of straps instead of chains and not positioned to adequately secure the loader in the event of the trailer tipping over.
May require C1E or CE licence category depending on how the towing vehicle is registered.
Not referred to in the tweet, but carrying the van probably ought to be done on white diesel.