This flower is growing in my back yard out of the wall. I've tried Googling "purple flower yellow center" and similar terms but I can't find an exact match.
I'm in North-East England if that's any help!
This is Kenilworth Ivy,
or, scientifically, Cymbalaria muralis. It loves to climb on walls and brickwork ("muralis" signifying "wall" in Latin). I did not know until now that it is considered (by some) to be medicinal.