But far more sophisticated machines are being developed. The National Health Service has used a robot called da Vinci to perform surgery at Guy's and St Thomas' NHS Foundation Trust in London. In Japan, human-like robots such as Honda¡¯s Asimo and Sony's Qrio can walk on two legs. More advanced versions are expected to be undertaking everyday domestic tasks and helping to care for the elderly in as little as 20 years.

"I would hope they would always be subordinate," said Brian Aldiss, the science fiction writer. "But one will no doubt come to rely on them deeply." Aldiss's short story Supertoys Last All Summer Long was the basis for the Steven Spielberg film AI, which addressed the subject of whether androids that have become as intelligent as humans should be denied equal rights.

Other dilemmas may arrive sooner than we think, says Christensen. "People are going to be having sex with robots within five years," he said. So should limits be set on the appearance, for example, of such robotic sex toys? The greatest danger, however, is likely to lie with robots that are able to learn from their "experiences". As systems develop, robots are likely to have much more sophisticated self-learning mechanisms built into them and it may become impossible to predict exactly how they will behave.

"My guess is that we'll have conscious machines before 2020," said Ian Pearson, futurologist-in-residence at BT. "If we put that in a robot, it's an android. That is an enormous ethical change."

To critics who scoff that intelligent robots are a long way off, the roboticists easily riposte that machines can already exert surprising influence over our lives ¡ª think about the influence of the internet.