In my opinion the greatest fellrunners of all time are Joss Naylor and Helene Diamentides.

I personally have always preferred long solitary runs through the hills rather than races (although I've done my fair share) so I suppose my opinion is slightly swayed this way.

However if race performances are taken as the main criteria then I would say Billy Bland and Angela Mudge.

Incidentally Angela is one Briton who has performed at top level in many different parts of the world