Many sellers will tell you that their Hobby, Tabbert, Roma, Fendt, LMC, Lord Munsterland, (and possibly others) caravan is legal to tow with a Transit sized van, large 4x4 etc, this will usually only be true with the smallest models, the twin axle models are almost always illegal to tow with your vehicle.The majority of these caravans are 8 feet wide and require a commercial vehicle over 3501kgs to tow them with e.g. a vehicle on permanent tachograph.
These caravans usually belong, or have belonged to travellers and their families, and most caravans, certainly the newer ones are very well looked after, and are very spacious and high quality, after all, they are their homes. They also make excellent site vans when permenantly pitched, and are excellent for families as an cheaper alternative to a static caravan.
If you use your small commercial or family vehicle you will probably find that your insurance is invalid leaving you open to a hefty recovery bill, fine and penalty points should you be stopped or involved in an accident.
The legal size limit for touring caravans is 23ft long (not including drawbar) by 7 feet 6 inches wide. Anything over this size requires a vehicle over 3501kgs to tow it with.
This information is often discussed on the Hobby caravan forum.
I hope this information prevents some of you from unfortunate run ins with the police and vosa