Good morning, I'm hoping someone can identify this wretched weed for me.

It's stout, sturdy: the stems are bright red: the leaves are long and quite narrow (not linear) and appear in pairs up the stems, and are green with a red central vein underneath.

It has just started appearing this year, so the ones I have are all less than a foot high, but it goes quite tall, er, about three or four foot high from memory.

I can't remember what sort of flowers it makes - I try to get them all out before they get to that stage! - and most of the weed identification sites seem to go with flower colour first. But the stems are ridiculously red, rhubarb coloured, so I'm hoping someone might recognise it, or at least give me some suggestions.....

It's so common that I feel a fool for having to ask, but I can't find it in any of my gardening books, and I've had no luck on google either.

The sticky post asks us not to post photos, so I'm now trying to work out how to get the photo that I have onto the internet for you - in the meantime, does it sound familiar?

Please advise!

Rachel