Purple Hairstreak - context, Heeswijk-Dinther, Netherlands

Only after identifying it do I realize how lucky I was to see it. It's not an uncommon butterfly, but uncommon to see. They spend most of their lives high up in oak trees, their host plant. Only during very hot and dry days they may come down, and typically only late in the afternoon or early in the evening. This photo shows its easy to miss as it's quite small. Closeup:

The big fail here is not realizing this at the time, because I would have tried to capture it showing their forewings, which has a beautiful purple glow to it.