Morning walk by the river

Monday
I went walking this morning from the locks at Bois-le-Roi for a change. I didn't see any river traffic the whole of my outward walk, but on the way back there were a couple of barges and a pleasure cruiser. My collage shows a couple of the riverside mansions - the biggest one has now been converted into several apartments - as well as some of the barge traffic and a huge wildflower - can anyone tell me what it is?