It is a controversial subject which has, until recently, been treated with widespread scepticism.

But scientists at the University of Southampton have spent four years examining more than 2,000 people who suffered cardiac arrests at 15 hospitals in the UK, US and Austria.

And they found that nearly 40 per cent of people who survived described some kind of ‘awareness’ during the time when they were clinically dead before their hearts were restarted.

One man even recalled leaving his body entirely and watching his resuscitation from the corner of the room.

Despite being unconscious and ‘dead’ for three minutes, the 57-year-old social worker from Southampton, recounted the actions of the nursing staff in detail and described the sound of the machines.

“We know the brain can’t function when the heart has stopped beating,” said Dr Sam Parnia, a former research fellow at Southampton University, now at the State University of New York, who led the study.

“But in this case, conscious awareness appears to have continued for up to three minutes into the period when the heart wasn’t beating, even though the brain typically shuts down within 20-30 seconds after the heart has stopped.

“The man described everything that had happened in the room, but importantly, he heard two bleeps from a machine that makes a noise at three minute intervals. So we could time how long the experienced lasted for.

“He seemed very credible and everything that he said had happened to him had actually happened.”

Of 2060 cardiac arrest patients studied, 330 survived and 140 said they had experienced some kind of awareness while being resuscitated.

Although many could not recall specific details, some themes emerged. One in five said they had felt an unusual sense of peacefulness while nearly one third said time had slowed down or speeded up.

Some recalled seeing a bright light; a golden flash or the Sun shining. Others recounted feelings of fear or drowning or being dragged through deep water. 13 per cent said they had felt separated from their bodies and the same number said their sensed had been heightened.

Dr Parnia believes many more people may have experiences when they are close to death but drugs or sedatives used in the process of rescuitation may stop them remembering.

“Estimates have suggested that millions of people have had vivid experiences in relation to death but the scientific evidence has been ambiguous at best.