But the cider allegedly spiked with the sedative Midazolam by Kevin Cobb would have tasted just like raw West Country scrumpy, according to drugs expert Professor Alexander Forrest.

Cobb, 38, is said to have used the powerful sedative on Susan Annis, 31, when they were on a training course together at the Royal Brompton in 1996.

He is also charged with using the powerful sedative on three women patients at St Peter's Hospital in Chertsey. The women have already given evidence in the trial alleging that Cobb drugged and raped or sexually assaulted them.

Professor Forrest told the Old Bailey on Tuesday that Miss Annis suffered "a double whammy" and died when the drug combined with the alcohol and her heart condition.

"A person given Midazolam intravenously would fall asleep at a concentration at around a third found in Miss Annis' blood," he said.

Professor Forrest said he carried out a series of experiments on himself drinking half a dose of the drug in half a can of Scrumpy Jack cider .

Miss Annis had drunk two and a half cans with Cobb in his room at the Royal Brompton Hospital minutes before she collapsed and died.

However Professor Forrest said he could not rule out the possibility that Miss Annis was injected with the drug. Two students who tried to revive her saw two syringes by her body.

"My conclusion was that it was more rather than less likely it was given by mouth but I cannot exclude the possibility that some or all of it may have been given by injection."

Midazolam was also found in the bloodstream of a patient who said she went into St Peter's Hospital with abdominal pains and awoke on a trolley to find Cobb raping her.

Professor Forrest said the symptoms described by the two other patients allegedly drugged by Cobb were consistent with the use of the sedative and not sexual fantasies.

Cobb of Michaelman Close, Yately, Hampshire, denies 11 charges, including two of rape and one of manslaughter.

The trial continues.