The Hybrid Bluebell is a frequent garden escape. It is a cross between the native Bluebell (Hyacinthoides non-scripta) and the true Spanish Bluebell (Hyacinthoides hispanica), which is not usually found in Britain.
The Hybrid Bluebell has larger and more erect flowers than the true bluebell, which are arranged spirally around the stem (true bluebell flowers are one-sided). These have blue anthers, whose filaments are fused to the petals at the middle of the lobe. The flowers can also be white or pink

Inside of flower, showing blue anthers, and stamens attached midway along petal lobe