Can Anyone Shed Any Light?

Hi, can anyone identify this weed? The piece here is pretty small and most of it in my garden is but it can grow bigger and quite tall if left. It grows fairly quickly but I wouldn't say it's voracious. It pulls up very easily. Hope someone can help! No-one I've shown it to so far has any ideas. It looks like a small (whisper it) Japanese Knotweed

 

Welcome. Sorry, but I don't know what it is but it isn't Japanese Knotweed. Knotweed has a distinctive zig zag in the branches.

 

Yes, definitely not knotweed - it never actually comes through with small leaves like that - it starts as it means to go on - big leaves!

 

Japanese knot weed is easily identified by the main stems. To the eyes of the average gardener. The main stems resemble those of the bamboo family, with very pronounced joints. The stems are of a moist nature, similar to rhubarb stalks.

There are several plants from the same genus, including. Russian vine etc. The flowers of both are identical.

 

Could be a clematis shoot.

 

is this knotweed ?

 

Looks like Impatiens @Flumpy
Himalayan balsam.