Whilst observing the nest, I was astounded to see this occur. A female Common Kestrel flew in and spent a long time perched opposite. It very quickly realised a nest was in the vicinity due to the noise the young Lesser Spots were making. The Kestrel gradually got closer and closer to the nest-hole and following one trip in by the adult female, flew to the hole and smothered it with its open wings. Fortunately, it was not capable of reaching into the hole and eventually flew off. Never thought of Common Kestrel as being a possible predator of Lesser Spotted Woodpecker!