A plant like Her Bennet but with red flowers

Sorry, I don't have a pic because my phone is old and crappy and there's no way to upload to my laptop.

A client has a single plant that (which she bought from a garden centre) and it has one red flower left but the rest of the heads have turned to burrs that are absolutely identical to Herb Bennet/ Wood Avens.

The leaves are long and frilly leaves a bit like Asplenium scolopendrium.

Any idea what it is?

 

The only things I can think of are a form of Potentilla or a Geum.

 

Thanks for your replies guys.

Going to de-head the plant next visit. She's a new customer and no doubt will end up with them everywhere and a lot of work for me if Herb Bennet is anything to go by. The seed heads and burrs are indistinguishable from Wood Avens (which her borders are already full of) and we all know how quickly they spread....