Herbicide. Home garden contact weedkiller.
Use on gravel or brick drives, terraces, walkways, pathes and patios, decking, paving slabs
Also use on concrete, asphalt, along fences, walls and on waste ground
B&Q and Homebase are selling this at £5.98, and even comparision to some of the instore brands, this is cheap!
NOTE: But just beware, its not a root killer...its more of an instant fix than a long term solution.