I was going to say Hart's tongue fern [Asplenium scolopendrium] but the top of the fronds are unusual. I will have a read up in my book!

Edit - looks like "Scolopendrium vulgare sublineato-striatum" So a variety of the above.

yes I agree. its a good doer Bulbaholic. I have it in my garden too.

Thanks, Kildermorie. I can't find any info on the ssp. but will accept your word for it.
Certainly a good doer, Sbg, it is a venerable plant and thrives on neglect.