It may not seem like a big deal to you, to see a Brimstone butterfly, but here in Wales I have only seen TWO in all the 23 years we've lived here. One last year, and one TODAY! You have NO IDEA what a smile it put on my face. I don't think we have much Buckthorn here in Wales, which is what the Brimstones feed on.
HERE is a link to a photo (and some wonderful photos of other butterflies too).
The photo at the top is Llyn-y-Fan-Fach again, or rather the approach to it.