Dr Camilla Nord, a neuroscientist at the University of Cambridge, disputed these claims. She said the Lightning Process was “right that the brain can create symptoms of physical ill health” but added: “I think it’s a wild claim to say there’s nothing wrong with your body.”

She believes there is a place for therapies that calm the body’s stress response and adjust how people react to their symptoms. But even if some symptoms are based in the brain, she added, that didn’t mean it was “something that you can actively change”.

The coach on the course stressed the importance of avoiding negative thoughts and words like “pain” and “fatigue”, claiming using them can continue symptoms.

“I’m afraid now we’ve strayed very, very far from neuroscience,” Dr Nord says, calling this an “abuse” of scientific terms.

When we put these specific claims to Dr Parker, he said our questions seemed to be “informed solely by the rumours and misinformation” circulated by what he called “anti-recovery activists”.

Long Covid support groups told the BBC’s File on 4 programme that a lack of consistent services for patients is leaving people with nowhere to go.

Of the 90 trusts running long Covid services in England, about two-thirds (58 trusts) responded to Freedom of Information requests asking for details about their provision.

Of those, seven had at least one full-time doctor on staff. Eleven said they could not order tests or scans, while 24 said they could not prescribe drugs.

Prof Altmann, said: “There are hundreds of thousands of dissatisfied, desperate patients who never get to meet any doctor.” He said the long Covid clinic coverage was “uneven” and had become a “postcode lottery”.