A flower that arrived by accident

Honey garlic, allium siculum. 

In the places where this is common, the Black Sea and Mediterranean, it grows in woods. It likes damp and shade. It appeared on my allotment when I was working at the University of Surrey as a Royal Literary Fund Fellow. So, sometime between 2010 and 2012. 
I remember asking in the office, excited by this exotic droopy plant with gorgeous flowers. 
It arrived just like that and it's multiplied where it appeared and moved to the top of the plot where it grows among spring nettles, holding its head of flowers above clumps of stinging leaves, among the brambles. I leave the patch untouched because the robin, or a succession of them, always nest in the tangle of thorns. It's safe. 
The plant's other names are Sicilian honey lily, Sicilian honey garlic and Mediterranean bells. It's a bee plant and it's multiplying in the dry, chalky soil where it first appeared. I designated this a flower patch so I don't dig it over much, although this year I've had to pull out a lot of grass and Japanese anemone which is taking over. The ox-eye daisies too are rampant. 
Below this patch is the even drier lavender patch where I've also planted sunflowers and angelica. On the path side is a vine. 
When I see the buds of the honey garlic opening I realise how little I know. They open like moments when I read a poem and am somewhere else. They open like mistakes, accidents, chance encounters. 
And as they spread, I am less afraid of destroying them forever. 
Where did the first one come from? I've looked forward to it coming back now for nearly a decade.