Without a closer view it is a bit difficult, but from here it looks suspiciously like Carex pendula. If it has three sided stems them that is the way to id Carex. If it is, then it is a thug of the first water. Don't ever let it flower.

Many thanks. It has indeed 3 sided stems and from other pics posted online that's what it looks like. Think I have a job on my hands. Any tips on getting rid? like pronto!

Garden fork! Or Roundup painted on the leaves so you do not damage the surrounding plants.

Have just now cut it right down to as near to ground level as possible. And yes OB it definitely is a thug of the first water. Had to wear gauntlets or risk losing some fingers on the stems. Soooooo strong. Had enough now....tomorrow I'll get the garden fork and see what damage I can do with that. Appreciate your comments. ;-))

I would cut off and burn those flowering stems to make quite sure too.

I just dug up a huge clump of this in the middle of a clump of crocosmia under a Mahonia, so well hidden. I didn't notice it at first and then saw a couple of the pendulous seed heads which went straight in the incinerator. This will take over your garden given the slightest chance.

I love the casual way you said that - it must have been quite a tricky job!

This plant is tricky Stera. It'll cut your fingers given a chance and you have to dig right down to get it all out. A tough job in this weather especially. Plenty of water round the roots to loosen them up, a lot of pushing and pulling and hey presto. I noticed a smaller version round the back of the Mahonia so a repeat performance to follow!

I have a couple waiting fr the death sentence - keep putting it off, I wonder why...