[edit] Oops - saddad's already talking about it here (http://www.allotments4all.co.uk/smf/index.php/topic,53808.0.html).
I can't see Saddads thread (perhaps it's on another section).
Watched an item on breakfast TV about the knot weed this morning.
Drove to work and thanks to the report, I recognised it all around the car park, on land belonging to London Underground (Central Line).
According to the report, it's roots reach a depth of three yards and covers thousands of acres.
I imagine the furore is whether to introduce a species of insect into the country to combat it, the scientists stated that they only live on knot weed,
and tests are more stringent than they were previously.
My thread is called aliens... but the hyperlink "here" on unwashed's comment takes you there... :)