The street where I live has gone purple

We all know that plants grow in the oddest and most unusual places.  They have a mind of their own, do their own thing and some don’t need any looking after at all.  In fact, it’s a wonder they survive but, survive the do.

I live in an established tree lined road, with Victorian and Edwardian properties.  Most of the original boundary walls are still in situ and built using stones and a type of gravel and cement mix.  It a lovely road, and made all the more so when a beautiful little blue/purple flower spreads its way down the street bursting out of  all the nooks and crannies in the walls.  It appears this time every year. I don’t know what it is called but wondered if it was an Aubretia, although I am not sure, the flowers seem the wrong shape.      There are a few variations, as you will see from the last photo.   It’s such a picture, seeing this delicate but clearly robust flower steadfastly growing and giving great colour to the road.  If you recognise it please let me know. Update: Since writing this post, I am reliably informed that this is Campanula.