Royal were marketed by MRC If I remember right for a number of years (Maybe it was Altech?). Over the years they were made by 3 different companies.

The last ones were made by LEO of China and were copies of the OS 46SF series of engines. They were a moderately powerful ball bearing engine and they didn't give much trouble.

Just Engines in Great Britain in recent times sold LEO's and also under their own brand of J'EN. I don't know if the current J'EN engines are LEO's or SK's