Nectarine planting

I don't know when this tree was planted. No-one will own up to planting it and chances are it grew from a seed tossed at the bins and missed, or something like that. Regardless of provenance, by 2006 it was flowering and fruiting. In 2007 I took good care of it. It's been pruned most years, it has mosaic disease exacerbated by being a tree growing in a tiny courtyard and not getting enough breeze, but it's pretty sturdy and fights the disease off every year. The fruit is sharp, refreshing and incredibly sweet if I can keep the birds off long enough for it to ripen on the tree. I didn't prune it in 2014. that paid off in fruit but the tree canopy is shading all but a sparse square metre of the garden.