Under the Shade of the Old Oak Tree

At the bottom of our garden, there is an area which is overhung by a large spreading oak tree, and underneath it in the early Spring these beautiful bell shaped flowers appear. I have no idea what they are, they look a bit like snowdrops, but the plants are far too big, and the flowers hang on long stems in twos and threes. If anyone can identify them, I would be grateful, and I thought I would take a shot from underneath, looking up into the branches of the oak against the blue sky. I hope you like it