Pineappleweed

Matricaria discoidea. This was growing happily in the gateway of a farm along the lane. If you squeeze the flower heads they give off a pineapple scent.
Apparently this plant was introduced to the UK from Oregon in the late C19. It is related to camomile and has a long history of use in herbal medicine. The flower heads can also be used in salads - I will try one tomorrow...