I have the same plant...i got them for £1 each in the bargain basement section. It's an Aster but can't remember which one

Oh, thank you Badfish. Quite unusual, isn't it?

Is it Aster Divaricatus (Woods Aster ) ? Does anyone know ?

It doesn't look the same as my Aster Divaricatus (see picture on my photos), the centres on yours look pink whereas on mine they are more brown.

Hi it looks to me like A lateriflorus "horizontalis", Derek.

Thanks everyone. Mine has only been in flower for the past few weeks if that's a clue?? I don't even remember buying it, otherwise I could look for a label amongst the large pile in the greenhouse . . .

I have just Googled A. lateriflorus 'Lady in Black' which matches mine exactly - so thank you Derek, spot on!