Flintstones on course (sorry could not resist)
Here what i could find
"UK -- Here's what's been unflatteringly described as a "garden shed on wheels," a British motor vehicle museum says this 1908 caravan (travel trailer to us folks in the US) is the oldest existing recreational vehicle designed to be pulled with a car.
Visit the Motor Museum in Llangollen, Denbighshirem to check it out for yourself.