What is this?

[AV76]

Please can somebody tell me what this plant is popping up around my garden? It is tall and this and has small light purple flowers in a kind of plus shape, with long thin leaves.

Flower-Only hosted at ImgBB

Image Flower-Only hosted in ImgBB

ibb.co

Flower-Stalks hosted at ImgBB

Image Flower-Stalks hosted in ImgBB

ibb.co

Thank you.

 

[Oliver Buckle]

It looks like a speedwell, there are a few, try 'Germander speedwell'.

 

[DirtMechanic]

Look up willow herb and see what you think. Epilobium tetragonum.

 

[Oliver Buckle]

I see what you mean. I had thought that when I saw the seed, but I hadn't realised there were varieties with single flowers like that.