ID needed please

I have a couple of patches of this growing in my garden, I hope it isn't a weed as I rather like it! I have seen it growing from brickwork all around Blackpool, so I guess it likes lime and salty air!

 

It is a Campanula probably the one which used to be called C.muralis, but not sure what it is these days. It could also be C. poscharskyana. Both of these are rather rampant growers so do be careful.

 

Its lovely. Whenever I see it I always think of Campanula poscharskyana. I am not clear what the difference is between C. poscharskyana and C. murabilis (also known as C. portenschlagiana)?

I find it makes nice little mounds and is pretty well behaved. It self seeds a bit, but is always welcome as I use it as edging to the border.

 

Brilliant many thanks I am going to get hold of some seeds from it and plant so it can drape over the walls in my garden

The specimen in the photo is growing out of the tinyest crack in the floor!! Wish I could move it, but no chance of that lol

 

C portenschlagiana was introduced by Will Ingwersen, a great Nurseryman and he is reputed to have said that he wished he had never seen it in the wild never mind introduced it. It can be a terrible thug by both root and seed.
I think the other one has dark blue, more bell shaped flowers.

 

Thanks Palustris. I looked it up in my book, but the description for both was essentially identical, and they both come from the hills of Croatia. So I haven't a clue what mine is. I love mine and don't find it a bit thuggish. But I think whether a plant is a thug or not depends a lot on your soil and climate. I grew some Campanuls takesmana one year from seed. I was aware that it was regarded as a thug, but my plants all died out by the second year - I think I got the wimp seed strain. :D

Thanks Marley for the comments about the different colours. I thought it only came in the one colour. I will have to keep an eye out for the others.