Bwlch y Groes is the highest motorable pass in Wales. A sort of "Welsh Khardung-La". Of course, as soon as motorized vehicles existed, people tested their vehicles going over it. As of the writing of this article in 1912, a 6hp Royal Enfield (for which nothing was impossible) was one of the two sidecar combos that had passed it, although a little spat arose between readers concerning priority. Triumph and Morris would later use it to test their vehicles.
The Belgian Army was supplied with Royal Enfield motorcycles. Here is a rare picture of one of them, which The Motor Cycle goofed and labeled as belonging to the French Army, having to issue a correction later. Jan 27th 1916.