A roar of laughter erupts from a crowd inside a large conference room at the De Vere Cranage Estate hotel. The joke? The idea that visiting the doctor could help treat a serious illness.

On stage the controversial Australian proponent of natural remedies Barbara O’Neill is taking part in a question-and-answer session during a five-day wellness conference, where science mixes uncomfortably with Bible verse and potentially deadly pseudo-scientific practices.

She is advising people attending at the event in Cheshire on a variety of medical ailments, and dismisses the use of antibiotics, vaccines or scientifically proven cancer treatment.

Tickets for the residential retreat can cost up to £1,300.…