Mysterious Yellow moth is a Yellow Belle

Spot the moth center picture above.

 I've searched my books and the Internet and have yet to identify it.  It was a fast flyer and very colorful as it flew over the South Downs of East Sussex yesterday.

What is it?  Please let me know if you recognize this little beauty.  It was very striking in bright sunshine.
Footnote; Thanks to http://www.sussex-butterflies.org.uk/index.html I'm now informed it is a Yellow Belle.  See also http://butterfly-conservation.org/51-1584/yellow-belle.html