Which weedkillers have you tried? and you seem to be saying that the alchemilla is growing on what's classed as the public highway (pavement, road, etc). It is actually illegal for home owners without a licence to apply or use weedkillers on the public highway or public land, so really, you should contact your local council about what's there. If the road is unadopted by the Council, then you can legally use the weedkiller.

If you have it growing in your garden, in borders, then its easily dug out, but you should keep an eye out for all the seedlings and remove those as they appear over time. If you want to keep one or two plants, make sure you deadhead before seed forms to prevent further spread.

For those growing in cracks and crevices on paving and paths and the like, if you cannot scrape them out, then applying a path weedkiller twice a year such as Pathclear will sort out most of them. The optimum time for such a treatment is April, and then again in July, when the weather is dry but the weeds are growing. Pathclear and similar products intended for hard areas have a residual effect up to 3 months (they often say 6, but I find its only about 3), unlike other products such as Roundup, but they must not be used on planted areas, nor any excess allowed to run off into planted borders/beds.

Thanks so much i will try your suggestions in April, have it on ny calender.