A nutty weed?

A nutty weed?

Observation - A nutty weed?. Description: I spotted this 'weed' in my window-sill chives a few weeks back and only got round to weeding it today, but on plucking it out it's sprouting from a nut of some sort, which I'm sure I didn't plane, and the root seems fairly substantial. The nut is about

I spotted this 'weed' in my window-sill chives a few weeks back and only got round to weeding it today, but on plucking it out it's sprouting from a nut of some sort, which I'm sure I didn't plane, and the root seems fairly substantial. The nut is about an inch long, and to my untrained eye the leaves resemble young holly leaves. Any ideas?