Knightscope K5
Earlier models of the Knightscope patrol robot had a major design flaw: they couldn't stand up after being pushed over Knightscope

Computing giant Microsoft is one of the Silicon Valley companies that has hired robot security guards to protect and serve the streets around northern California's technology hub.

The Knightscope K5 robot security guards are fitted with lasers, GPS and heat-detecting technology, and can predict where criminals will strike next and the likelihood of future crimes.

Knightscope K5
Unlike human security guards, the egg-like Knightscopes are not armed Knightscope

The 5ft tall robots are designed to operate without human control and are equipped with surveillance cameras and sensors, a thermal imaging system, scanners that can read 300 car registration plates a minute, and odour detectors. It patrols the streets using lasers to gauge distance and a GPS system.

The robots analyse information from government, businesses and social media sources to predict the likelihood of a crime being committed in a given area, and decide whether the alert authorities it if comes across anything suspicious.

Four of the robot security guards have been deployed to guard Microsoft's Silicon Valley campus, in the system's first real mission.

It appears to be going well, although the robots have come unstuck in the face of a seemingly innocent adversary: steps.

Rachel Metz, a reporter for MIT Technology Review, said: "I noticed that a K5 in the distance had somehow toppled over the edge of the sidewalk onto the parking-lot asphalt several inches below. A couple of Knightscope folks were needed to pull it upright."

Well, if Doctor Who's mortal enemies can't handle stairs, what chance to these youngsters have?