One of the six volunteers who fell seriously ill when a clinical drug trial went wrong is showing early signs of cancer, according to a report on Sunday.

In an interview with the Mail on Sunday, David Oakley, 35, said his life had been on hold since doctors told him he had an “aggressive” form of the illness.

“It’s very frightening,” he said. “I am trying not be too down about the thought of having chemotherapy or that I might die. I can’t work or make any long-term plans. We live from day to day and hope that when the cancer develops, it will be treatable.”

Oakley, a driving instructor from west London, suffered a life-threatening reaction to a drug during an early-stage clinical trial in London in March. His head swelled and his organs failed.

He said doctors warned him that he risks developing multiple sclerosis, arthritis and chronic fatigue.

The trial of TGN 1412, designed to treat chronic inflammatory conditions and leukaemia, was conducted on behalf of German firm TeGenero by contract research firm Parexel.

A spokesman for Parexel was not immediately available for comment.

A volunteer who was given a placebo, or dummy drug, described how the other men were writhing in agony, vomiting and screaming about the pain in their heads after taking the drug.

An interim report last month by government-appointed experts said the first dose of such drugs should only be given to one person during early trials.

Oakley said he took part in the trial to raise 2,000 pounds for his wedding to his then fiancee Katrina, 29.

“What had seemed such a safe bet almost killed me,” he said.