A hospital is helping scientists go beyond the grave and understand what happens after patients die.

The Croydon University Hospital trust is one of 25 medical centres across the world taking part in a study to find out what happens to the human consciousness when people die.

Russell Metcalfe-Smith, clinical lead for resuscitation, is in charge of the study, which has been going since 2008.

The 34-year-old has been responsible for bringing many people back from the brink of death after a cardiac arrest.

He has spoken to those he has helped bring back to life to find out if they saw or felt anything when clinically dead.

The hospital has shelves fixed above beds, with images on them, and the idea is if someone has an out of body experience, they should be able to describe the picture.

He said: “People often feel they are floating above themselves and can see what is happening.

“We have had a number of people who suggested they have experienced something, but we have not had anyone who has seen the picture that is facing the ceiling.

“Some can remember people around them, some remember what people were wearing. One patient reported being in the room but being unable to get out of a window and then feeling they were coming back into their body.”

Dr Sam Parnia from the US, who is hoping to publish the results of his Aware study next year, is working on analysing the data from more than 1,000 patients.

He said: “Resuscitation is a relatively new science, it has only been around for 50 years. Before that, people died.

“What we have learned is death is reversible in the early stages.

“We have found between 10 and 20 per cent of survivors who have come back from death will have memories, some kind of cognitive state while clinically dead.”

Dr Parnia refused to speculate on the results of his study but said many people interviewed had similar experiences.

He said: “The evidence that is interesting to me is that, contrary to my training, the entity we call the human mind and consciousness appears to continue to exist during the early stage of death.”