For a machine that looks like a cross between a vacuum cleaner and a Dalek, RP6, Britain's first robot doctor, has a gentle bedside manner. But then it is fitted with an image of the doctor on its "face", in this case Parv Sains, a surgical specialist registrar at St Mary's Hospital, London.

The Remote Presence 6 - nicknamed "Sister Mary" - is one of two robot medics performing ward rounds in a telemedicine trial at St Mary's.

Gliding from bed to bed, the robot does not physically examine people, but is fitted with a video screen that allows patients to communicate, face-to-virtual face with the doctor who performed their surgery or specialists anywhere in the world. The doctor controls the robot with a joystick. Cameras allow them to see the patient and ask questions.

Mr Sains said: "Our robots would never replace all doctors on ward rounds, but they are a communication tool which allows a doctor to have direct contact with their patient.

"If we look at the current strains on the NHS, many senior doctors with specialist skills and knowledge are required to be in several places at once. This allows them to log on, see the patient and make a decision."

The trial will test how patients respond to the £50,000 robots. If all goes well, they could be deployed in the accident and emergency department to assess urgent cases.

"It's all a bit Star Trek, but if you look at how robots are used by the military and industry there's no reason why the NHS can't move in that direction," Mr Sains said.

Tara Fairall, 28, who is recovering from a gall bladder operation, is one of a few patients "examined" by the robot. She said: "It's weird at first but you get used to it because it's like talking to a doctor. The doctors can't get down quickly enough when you bleep them sometimes, so at least this way you get to talk to someone."

Mr Sains said: "If a specialist is at a conference in California but their medical opinion is needed for a St Mary's patient or to deliver a lecture to junior doctors, the RP6 robot provides an instant and global link. People have asked why we couldn't just use a webcam mounted on a trolley but then someone would have to push it around and focus the camera. We don't want it bumping into patients."

Quicker decisions about when to discharge people after operations would reduce bed blocking, Mr Sains said, and the technology could give smaller district hospitals without in-house expertise faster access to specialist advice.

Not everyone was impressed. "I'm not remotely familiar with technology and I don't think I'd like it at all," said one elderly woman in the ward. "I think I'd come to the end of everything if I was sent a robot. I mean, where are all the doctors?"

Nor is the technology foolproof. Sister Mary had to be given a very unladylike push when the Guardian visited yesterday - the wireless internet connection that controls the robot had failed.

The robots are used at three hospitals in the US, but this is the first trial in Britain.

In a further development, a robot surgeon has helped doctors carry out a kidney transplant at Guy's Hospital, also in London. The £1m machine plucked the organ from Pauline Payne's body with its two mechanical arms before conventional surgery implanted the kidney into her fiance, Raymond Jackson.

Although the da Vinci robot has been used before in the UK to remove diseased organs and perform simple reconstructive surgery, this is the first time a critical and difficult operation such as a live organ transplant has been attempted.

Two robot arms were inserted through 8mm holes in Ms Payne's body. The "hands", clasping instruments, then went to work, controlled by an operator nearby. The mechanical movements may be slower than a surgeon's hand, but the machine compensates for any tremor.

A third arm, passed through another hole, carried a small camera. The images were then viewed by the surgeon, through virtual reality binoculars, who also controlled the position of the camera with foot pedals.

Prokar Dasgupta, a consultant urologist at Guy's who led the surgical team, said: "It is a milestone, but we don't know all the answers yet. Removing a transplant kidney is a more precise operation than taking out one that is diseased.

"What we have achieved is a significant step, but one that is still undergoing scientific evaluation. We have to do more of these operations."