Would anybody know
what this weed is, and how I can get rid of it?
It seemed to start in the flower bed, which I had filled up with dug up soil from elsewhere in the garden. So I assume there is something in the garden soil. Anyway, it was a mistake to put that soil in the flower bed. In the past year not only has it been strangling the flowers in the flower bed but as you can see from those photos it has now grown over large areas of the hedge (which is not connected to the flower bed). I'm not quite sure why it has been spreading in the past year.
Thanks.