It looks like Campanula [ the Bell flower]

I know it as Canterbury Bells, elsewhere as Bells of Holland - Botanical name Campanula Medium.

Yeah, Julien, but there are lots of species of Campanula. Breda wants to know which one this is.
persicifolia? latifolia? rotundifolia?
Sounds like a shot of the leaves is required.

I don't think this one is canterbury bells (C. medium) as that has "chunkier" flowers with more definite turned out edges to the petals. This is more delicate, with tapered petals giving a more "starry" finish to the flower and not so bell-like.

I'd say campanula persicifolia but can't be sure without seeing the leaves. If it is this one, it should self sow so you can get more plants for free

Looks like Campanula persicifolia. Pretty blue colour.

This is the leaf of the Campanula about which I asked the question. I hope it is helpful and thanks a lot to all who kindly commented.

It was suggested that a picture of the leaf of my Campanula might be helpful so here it is. Hoping. And thanks to all of you who so kindly commented.

OK, I've found a new question here -
http://www.growsonyou.com/question/show/55946

with two pictures this time.