Interesting that they are talking about an illegal release when it hasn't been confirmed. There have been reports of lynx for decades all across the UK but few (if any) confirmed sightings (partly due to their nature).
So the options are: a) there might not be any lynx just a misidentification of a couple of big moggies, b) they are lynx but they are part of a breeding population that has been there a long time or c) this is actually an illegal release (but if so from where? Illegally releasing beavers isn't difficult as there are plenty around but lynx....).