If you didn’t know before you visited this site, you’ll know now that Japanese knotweed (Fallopia japonica) is a very invasive plant. It’s so successful as it was brought in from Japan, and over here it has no real competition or predators (though there might be a way forward with the use of psillids).
There are other invasive species in the UK, however, and these include the species shown below. You can find out about each one by clicking on the name, or see them all together in the Rogues’ Gallery page of the Canal & River Trust.
Visit the PLR Ltd London website for more information on Invasive species rogues’ gallery