I have recently done up my back garden. Prior to this it was a forest of weeds and ivy. There was always 1 weed which grows up to nearly 6 feet, I used to chop down every few weeks, but it would grow back to the same height again within 5 or 6 weeks. I have been unable to identify it, so therefore i didnt know how to kill it off. It is now coming up through my new lawn. Would you be able to identify it from the pictures below (which is it only as a shoot), and maybe tell me how best to eradicate it?