Can you identify this plant growing in pavement crack?

I found this tiny little plant growing at side of pavement and wondered what it is - any ideas?

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Re: Can you identify this plant growing in pavement crack?

Reply from Nicola

Hi Kirsty, a suggestion from our helpful followers on social media:

"Could be a small-leaved Ballota."

And another useful suggestion "That looks like 'Mind Your Own Business'; Latin name: Soleirolia soleirolii"

We hope that helps?
Plus a joke, it seems, "Pencil Thyme"?