Every householder has a legal duty to keep his premises free from rats.
Lay ready-to-lay proprietary baits. Or bait several traps but don't set them. Just leave them out for a few days, replenishing the bait as needed, until the rats get used to them as a food source. Then set them.
Secure dustbin lids and preferably keep bins on a rack off the ground and 2ft/600mm away from walls.
Plug cracks and holes in outside walls with wads of steel wool, then permanently seal with wire mesh or heavy-gauge sheet metal.
If you're still plagued by rats, call your Environmental Health department or a pest control company.
