I saw a rat in my garden once. It was in some need of some major gardening so I guess it was attracted by overgrown weeds and bushes and stuff. I cut back everything to make sure it couldn't make its nest anywhere then just put down a couple of rat traps like this: http://www.victorpest.co.uk/shop/rat-control/snap-traps Caught the rat and haven't seen one in the garden since!