Looks like it could be a Geum of some kind. I would leave it until it flowers next year and see if it is worth keeping or not.
On second look - the leaves at the top of the picture look like something different, perhaps someone else can help you further.

Excellent. Thanks Wendylongfo I'll leave it in and see what happens.

I suspect its probably Geum urbanum, a weed that pops up wherever it fancies, rather than a Geum such as 'rivale'. The slightly different leaves towards the top of the picture might be Aquilegia, hard to tell at this stage. If you've got others in the garden, then it could be, easily, though not to sure the leaves are entirely right.

If it is G. urbanum then don't let it go to seed or you will be removing it forever.

However a weed is simply a plant in the wrong place. Evening primroses and red campion are weeds here but lots of people in other places buy the seeds and grow them on purpose. Give it a season and see if you like what it does and then heave it out if you don't.

Geum urbanum is always a weed, in any place. You can tell if it is, if the flowering stem is tall and has lots of tiny yellow flowers. It flowered once in the back of our yellow border, unseen and since then I have had to pull out dozens of plants, every year, even though we have never allowed it to grow again.

the other plant in amongst the geum looks like a welsh poppy to me usually ornage or yellow flowers and they self seed freely also becoming a nuisance.

Yes, I hadn't quite realised I had two plants together but can see that now. I certainly have some other poppy-looking plants in the garden; yellow ones (picture added) which to be fair I quite like. I don't seem to have Geum anywhere else so may take the chance and leave - it's fate to be decided next year!

Thank you once again for your help - love this site, lots of helpful and knowledgeable people.

If you don't have Geum rivale in the garden nearby already, this one will most definitely be Geum urbanum, desirable Geums don't seed that easily, so I wouldn't wait for it to flower.

From the comments it looks to be a weed and one that's somewhat difficult to contain once it gets stuck in. Have therefore changed my mind and decided to take this out.