Fast-forward an hour and a half: Jayne is moving freely around the room, bright-eyed, smiling broadly and without even the tiniest tremor.

The secret? John is a laughter coach, and he had made Jayne laugh. By asking each patient to step to the front of the room and carry out simple role-play exercises — repeating the same number in any way they like, staging a bank robbery — John is a regular witness to the transformation of fear-fuelled patients into invigorated, buoyant beings.

Humour is first cousin to hope, it has been said — what we can laugh at, we can rise above. But Cremer’s work is not tailored just to the ill or the needy. Big corporations such as Legal & General, Bank of America and Airbus employ him and his troupe to work with employees in groups 200 strong, simply to reduce them to a state whereby 17 muscles contort around their mouths, their eyes are reduced to slits and they emit a series of short vowel-like notes, each about 75 milliseconds long and repeated at regular intervals, 210 milliseconds apart.

“A merry heart doeth good like a medicine but a broken spirit dries the bone,” runs the proverb. But a wealth of recent research has shown that merriment and medicine are more closely aligned than we had previously assumed.

Dr Lee Berk, associate director of the centre for neuroimmunology at Loma Linda University Medical Centre, southern California, is one of the world’s leading authorities on what he calls “mirthful laughter” — “happy laughter as opposed to coping laughter or black or derogatory humour”.

His most significant research on the healing effect of laughter is in the field of psycho-neuroimmunology, which looks at the effect of the mind on the brain and the immune system.

Since 1990 Dr Berk’s laboratory has been acquiring cellular and neurochemical samples from subjects via four measures: before, during and after laughter, and the next day. They have shown that laughter increases the number of activated Tlymphocytes and the number of T-cells with helper/suppressor markers, otherwise known as happy cells, which help to prevent infection. Some of these happy cells divide and secrete in a way that regulates or helps the immune response, while others are crucial for the maintenance of immunological tolerance.

Dr Berk’s tests have also found that laughter increases a type of immune cell called natural killer, or NK, cells, which go after virally infected and tumour cells.

“The method we used to test this was to take blood samples from the experimental group before and after mirthful laughter. We put the peripheral mononuclear blood cells in test tubes with a type of tumour cell line — and we found that laughter could, in some way, modulate a significant immunological cell like NK cells.”

Dr Berk might stop short of claiming that laughter is a panacea — but it should at least be taken seriously, he says. “I’m making quantum leaps here, but many studies have shown that for women who have breast cancer, those with better NK activity have a better prognosis. The activity of NK cells can be increased as a result of laughter. And if you have a population of individuals who are exposed to the same pathogen, why is it that some get sick and some don’t? I think it’s because immune systems are at different levels. So it makes sense to keep those systems optimised — and that’s when laughter starts to make a whole lot of sense.”

Although Dr Berk’s work is gaining recognition now, it was not always thus. When he started out in the Seventies, he submitted a paper to the American College of Sports Medicine stating that exercise could be beneficial to the immune system. It was summarily rejected.

“Now, of course, it is widely accepted as fact. I see laughter in the same light — it’s real biology.” And the biology is compelling. Over the past ten years, Dr Berk has carried out tests to show both that the immune system is optimised with the use of laughter, and that stress hormones are reduced by it. The latter could account for the IVF patients whose improved fertility was reported earlier this year. Using a professionally trained clown to make the patients laugh, scientists at the Assaf Haro-feh Medical Centre in Zerifin, Israel, found that the rate of successful pregnancies increased from 20 to 35 per cent.