Darwin's Berberis

These are the flowers of a Berberis,  a large genus of deciduous and evergreen shrubs found throughout the temperate and subtropical regions of the world (apart from Australia). 

This one from our garden is, I think,  Berberis darwinii a native of southern Chile and Argentina. As you might have guess, B. darwinii was discovered by Charles Darwin during the voyage of the Beagle. He collected it on  Chiloe Island, Chile in June 1834, and it was named after him by the foundation director of Kew Sir William Hooker in 1844.