Can anyone identify this plant, maybe a weed?

its one of our british natives and cant remember its name at the mo. so if you like it keep it, if not it is a weed. pull it out.
welcome to GoY too.

I think it's Echium Vulgare - Vipers' Bugloss. It blew into our garden once in this way. Bees love it.

hard to tell but it could also be one of the wild bugles Ajuga. the echium vulgare has stiff short hairs on the stem, the Ajuga either hairless or spft downy hairs.

Is it alkanet?

No, alkanet has big, rough leaves

That's definitely a Vipers' Bugloss. We too had one appear, it has lovely blue flowers with pinkish fine bits in it too (see technical terms here!). I was hoping it had seeded but no such luck. Give it some support in case of heavy rain as it grows quite tall. A beautiful plant.