Mystery bulb. Walking around the 'hood I passed a front garden where various plants had been left on the front wall including these bulbs. It has become a custom (round here at least) that if someone has something they wish to dispose of they leave it on the street and invariably a passer by gathers it up to put it to use. An informal and effective form of recycling which seems to extend to plants as well.

 I'm pretty sure these are Hyacinthoides hispanica aka Spanish Bluebell. They have a bigger bulb than our native H. non-scripta, grow taller and straighter with bell shaped flowers of a bluer hue than the Bluebells of our ancient woods. I planted them in a spot at the base of a shady section of the fence/ivy hedge so I'll see what results. Assuming they are Spanish Bluebells they will add to a number that were already in the garden when I moved in. As I am planting them 'in the green' they will probably not flower this year and take a year or two to settle in.

 I should note at this point that H. hispanica has a very bad rep among conservationists. It is said to hybridise with native Bluebells to their detriment. Indeed the hybrid of the two H. x massartiana is what the bulb trade has sold as Bluebells for a very long time; I would think they account for virtually all Bluebells in gardens. The characteristics of H. hispanica dominate, for example the hybrid is scentless. There is considerable angst that it will further hybridise with H. non-scripta.

 Having said that the Spanish Bluebell is a worthy plant in its own right which has been grown in this country for centuries. Variations on the Hyacinthoides genus occur on both the Southern European and North African sides of the Mediterranean in addition to H. non-scripta in northern France, Belgium and the UK. Interestingly recent research suggests that native Bluebells have much greater resistance to cross pollinating than has been supposed.

 Even so I wouldn't plant H. hispanica next to a Bluebell wood or in a rural setting. In central London that is not really an issue. The nearest extant colony of native Bluebells is in Abbey Wood about ten miles away. As far as I can see they are not mutating despite being surrounded by the metropolis.