What is the name of this violet type plant

Does anyone know what this plant might be? it’s a really troublesome spreader that has a complex underground root system and damages masonry when established. I’ve looked online and nothing quite answers the question. I don’t have the plant identification app that some do.

i did a check online came up as a Serbian bellflower

Thanks but not sure that’s the variety as this is not really a trailing plant. I had thought it was campanula but aside from the lack of trailing, it has a far less abundant flower show and tends to be a ground spreader. It’s likely related though. The root system is horrendous and it grows in the most inaccessible spaces.

It’s also not Campanula rapunculoides which although it’s considered invasive, has more bell-shaped flowers.