Rat trap came back

I've been clearing out an overgrown piece of garden - and lo and behold. We have reclaimed the walkabout rat trap, a full five metres away from where it was set. I've already met the rat that most likely did the walkie with said trap sconed on it's head. He's the size of a full-grown dog (as in chihuahua) and comes visiting from out of a drain 6pm-ish in the evenings.