It's a Mystery

I have been slatternly in my approach to our garden this year. I noticed this plant at the start of the school holidays and thought it was a weed- for some reason I also thought the flowers would be pink. It has now grown to monstrous heights( easily 7ft). yesterday my m-in-law, a lady with excellent gardening credentials told us it was not a weed but in fact a hollyhock. After internet research Floss says no.
Anyone else got any idea?