It takes years, but continual spraying with Roundup every time a leaf appears does eventually work.

Thanks owdboggy. I have just spent a whole day trying to dig up the weed and its roots from one of the borders. I will definately be getting round up for the other border. My neighbour neglects his garden and its full of the stuff hence it gets back into my garden via the roots and the seeds.

Fortunately the seed is over 90 percent infertile other wise....................
If it is coming in from outside, as it does in our garden, there is nothing much you can do but spray it every year, we have to. We did put a physical barrier between our garden and the roadside verge to try to stop it, but it has either come over or through it now, sigh.

Have been to the garden centre today and bought Round up weed killer. Will try on the remaining border. Dosn't come cheap does it, so hope it works. I t comes from under next doors fence so may have to offer to spray his too.