Does anyone recognise this?

Bill_and_Ben

I didn't plant it so it's a weed but I've no idea what!

nutcutlet

Alliaria petiolata, aka Jack by the Hedge and others. Food plant for the larvae of the Orange Tip butterfly

Bill_and_Ben

Thank you nutcutlet - that was a swift response. I'm now feeling guilty (on behalf of the butterflies) as it's in the green bin as it was completely obscuring my dicentra!