Northern Eggar on the wing 6/4/13?

On Saturday afternoon, the temperatures lifted enough for me to go on a walk around Mynydd Bodafon, with the aim of trying to find basking Adders. In a sheltered spot out of the wind, I found a Peacock butterfly on the wing, and a few minutes later a large orange moth flew past rapidly, in a zig-zag manner. Definately looked like a Northern Eggar, in a spot I've seen many later in the year. Seems very early for it to emerge though, just wondered if anyone else had seen one this early? Not an expert on their life cycle, looking in the guides it seems complicated! Here's one I photographed at the house in August last year.