The setting is during or after the fall of social order, somewhere in England. An old man is holed up on an estate, his only company a robot butler and other robotic assistants. The house is invaded by a gang of hoodlums, possibly a motorcycle gang. The robots and the man work together to poison or murder the brigands.
Published some time during the late 1970s, possibly the very early 1980s (1982 or earlier), the story appeared in a large format (not digest-sized) magazine and was accompanied by an illustration of the robot, which had a Union jack on its torso.