I have been unable to track down why this fern should be called the royal fern (Osmunda regalis), the best suggestion seems to be that it is due to its imposing size and stature. There is no reason why this should not be the case, of course, but it would have been far more interesting if King Peter the first had hidden behind one to avoid capture by elephants! What is interesting I suppose is that the royal fern may have derived its Latin name from Osmunder, the Saxon name for the Viking god Thor. Regalis implies regal so the common name seems to be a direct link to its scientific name. Why it is connected to Thor remains lost in time it seems!
The royal fern can be found right across Europe and favours damp, even boggy, wooded areas. In Dorset I have not found it that often but where it does occur it is likely to be present in some profusion. At the Dorset Wildlife Trust at Tadnoll there is lots of it near the Tadnoll brook. In general this a fern that is declining due to habitat loss from drainage schemes and past over collection.
It is not evergreen like some ferns, creating new fronds each year from the ever increasing clump of roots. This can make the whole plant extremely imposing as it grows with age. It is quite unmistakable for anything else, it is really a right royal fern!