George Stephenson introduced the dandy wagon in 1828, which was simply a four-wheeled cart supplied with hay, attached to the rear of a four-chaldron train in which the horse could rest on the downhill sections.
According to the Traveller's Guide (Blue Cover) [REF] Wagon number 50, a 4- wheel Iron Horse Dandy, built at Boston Lodge c.1861 was still in existence and stored at the Ffestiniog Railway museum as of April 1992.