Delivery takes between 30 minutes and three hours from the order being placed, although customers can also pick a two-hour window within the next four days.

Under conditions set for the pilot project by the German authorities, the robots are only allowed to travel in daylight, move at a normal walking pace on the footpath and are programmed to give way to oncoming pedestrians.

Media Markt charges its customers 14.95 euros for its existing express delivery service within three hours, but robot delivery could eventually allow them to cut costs and charges.

Starship, the company set up by the former co-founders of web call firm Skype that is developing the six-wheel self-driving robots, said each delivery by robot should eventually cost the retailer less than 1 euro once they move into serial production. It has not announced when that will happen.

For the trial, customers have to be at home to receive the delivery as the robot will send a message to their mobile phone to say when it is at their door as well as a code that will allow them to open the lid of the robot to get their order.

Germany’s Deutsche Post said earlier this year that it is testing robots that could help postal workers cope with increasing numbers of parcels on their delivery rounds.