Epimedium reticulatum
1st August 2009
Large yellow flowers which don't quite match the species description, and the leaves are not noticeably reticulate,
which makes me a little suspicious of the identification.
11th May 2013
References:
Barker, David G. - Epimedium and other herbaceous Berberidaceae, Hardy Plant Society, 1997
Stearn, William T. - Epimedium, 2002.