Damp. If its a private sale I suggest you take your own damp meter and know how to use it. 4 years old it should be ok but it wouldn't be the first 4 year old damp van.
Dont forget the freebies,awning,gas bottles,step,battery,water barrels etc..all this will cost you xtra if you dont get them with the van.Haggle on price.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.