Be CAREFUL what you think. That’s been the joke in my family – and with my autistic son’s teachers and carers – ever since he was a toddler.

David will know what you’re thinking. He can tell where you’ve hidden the things you don’t want him to find: presents, sweets, breakables. At times, it’s as though he’s telepathic.

‘He must be a mindreader!’ numerous care staff have told my wife Nicky and me over the years. ‘He just looks at me and knows what’s in my head.’

We laugh about it, because taking such notions seriously might seem slightly delusional. At the same time, we know it’s real. David seems to hear our thoughts.

Now a hit podcast has revealed that, far from being deluded, we are no different from thousands of other parents around the world with severely autistic children. Incredibly, telepathic ability appears to be a common talent among people who are often regarded as unteachable and ‘locked inside their own worlds’.

‘Nonspeakers who have autism are systematically dismissed,’ says presenter Ky Dickens, in her podcast series The Telepathy Tapes. ‘For decades, parents of nonspeakers have been told by doctors, educators and scientists that their kids are not “in there” – not capable of communication or competent of learning.

‘Imagine being one of those parents and discovering that everybody has been wrong about your child. They are in there, they are competent, and they can communicate. But then also discovering that your child can read your mind. Would you expect to be believed?’

I’ve never met or spoken to Ky, but she is summing up life for me and Nicky. Our younger son David, now 28, is profoundly autistic: afflicted not with the kind of, what I call, ‘celebrity autism’ touted by highly articulate and able people such as Gregg Wallace, but with the real thing.

Christopher Stevens with David in Snowdonia. The Mail writer says his son can read his thoughts

David has known what others are thinking since he was a toddler

David has been non-verbal for most of his life. Although he could parrot words, something psychiatrists call ‘echolalia’ or ‘speaking in echoes’, he was unable to communicate meaningfully. Two years ago, during a period of intense unhappiness when he was being mistreated at his previous care home, he had become completely mute.

Since then, thanks to intensive support from his outstanding new care team, and with innovative speech therapy, he is beginning to use a few words with real meaning.Some of the things he is saying have redoubled our conviction that David can pick up on thoughts.

When his much-loved grandparents died within weeks of each other last year, we decided not to try explaining to him that he could never see them again. He seemed to know anyway.

We saw him on the day before my mother’s funeral. At the end of our visit, instead of saying, ‘Bye-bye Mummy and Daddy,’ as he now always does, he fixed me with a serious stare and said, ‘Bye-bye Nanny and Grandpa.’

Stories like that are hardly scientific evidence, however sure Nicky and I are that David has plucked unspoken information out of our minds. The challenge for Ky Dickens, a documentary maker from Los Angeles, was to find ways to prove the telepathic powers of some of the most astonishingly gifted children.

She teamed up with Dr Diane Hennacy Powell, a neuroscientist who specialises in the study of autistic savants, people with exceptional aptitude for skills such as advanced mathematics or music, without having been taught. However, she was hampered by a lack of funding for research – most universities don’t want to give credence to paranormal theories.

‘The reigning philosophy in science is something called materialism,’ says Dickens. ‘This notion says all things in our world are the result of interactions between physical matter, things we can measure and observe. And research into telepathy falls way outside of the materialism lane.’

Dickens was eager to meet one of Dr Powell’s subjects, a Mexican girl named Mia. The 12-year-old was autistic and barely talked, but had learned to communicate by typing on an iPad.Mia could apparently pick up her mother’s thoughts, like a radio receiver. She also had an extraordinary memory for events when she was just a few weeks old, and even claimed to remember being in her mother Ileana’s womb.

Dickens brought Mia and her family to L.A. where she set up a complicated test. Mia and Ileana were seated on opposite sides of a screen, in a room with no reflective surfaces, so that no signals could be sent between them.

Mia donned a blindfold while her mother was shown a three-digit number, produced by a random number generator. Then the blindfold and partition were removed, and Ileana concentrated on the number: 698. Smiling, Mia took the iPad and typed, ‘698’. The partition was replaced and the experiment repeated . . . 20 times. ‘She was correct every single time,’ says Dickens.

Mia was also able to sort coloured lollipop sticks into matching piles with the blindfold on, providing her mother was there to see what was happening. She was not able to do it with other family members, including her father. It was as though, Dickens theorised, the child was not just reading Ileana’s mind but seeing through her eyes.

Aware that many people would suspect it was a conjuring trick, Dickens made a point of hiring a cameraman, Michael Agnesanti, an avowed sceptic. He was shaken by what he witnessed: ‘I’m watching her, I’m watching the mom, I’m looking at everything,’ he said. ‘It’s hard for me to believe this is not authentic.’

These experiments are repeated, in various guises, with numerous children, such as Akhil, a student in New Jersey, who can ‘receive’ words, numbers and pictures from his mother Manisha’s mind when they’re in different rooms.

Sometimes, she says, he will tune into her mind while she is shopping or watching television downstairs – and will later tell her what she’s been doing and thinking. That must be disconcerting.

As the podcast evolves, Dickens begins to explore even more disturbing aspects of the autistic mind, including the suggestion that these individuals can see and hear people who are invisible to everyone else, and perhaps communicate with the dead.

Merely touching on such ideas is bound to provoke explosive derision from sceptics. The Guardian calls it ‘wishful thinking’, psychologist Stuart Vyse, writing in the Skeptical Inquirer, describes the podcast as ‘a dangerous cornucopia of pseudoscience’.

Personally, I’m sceptical of sceptics. Often, their only aim is to convince themselves they are intellectually superior to anyone who questions the accepted science of the day.

It’s as though they are colour blind and, because they can’t tell the difference between green and red, refuse to believe in the existence of traffic lights. Worse still, they abuse and mock everyone who isn’t colour blind.

Not all of the more extreme claims in The Telepathy Tapes will prove correct, though all are worthy of serious investigation. But, for me, the irrefutable evidence of telepathy between parents and autistic children in this podcast has been a revelation.

Something my wife and I have suspected throughout David’s life is now a certainty.

We now have to work out how this can be used to help him communicate more effectively.

And for countless listeners whose assumptions have been overturned by The Telepathy Tapes, a host of new questions must now be faced.

As cameraman Michael Agnesanti asks on the podcast: ‘Do I have to believe in God now?’