If we came expecting reassurance from this bearded, 6ft 4in grandfather, the emeritus professor of physics who heads the Government’s mobile phone safety research, we are about to be a little shaken.

We begin by asking if this isn’t all a bit old hat. Haven’t we all got into an unnecessary lather about the dangers of mobiles, and wireless techno-logy? There are all these vague concerns — “There should be,” Lawrie Challis cuts in.

Oh. This is the more disconcerting because Professor Challis is one of the world’s experts on mobile phone radiation, and chairs the mobile telecommunications health research programme. He has some good news: the first batch of research it has done, soon to be published, confirms that mobile phones are safe in the short term, under ten years. But there is less good news. “It’s encouraging because they found nothing for people who’ve used phones for less than ten years, But there is a hint of something for people using them more.”

Now, being a respected scientist, Professor Challis is keen to emphasise that this “hint” remains just that. A massive European study called Interphone, partly funded by his group, found a slight association between the risk of brain tumours and using a mobile for more than ten years. But the problem is that the number of people involved was so small: more than a decade ago, hard as it to imagine now, we did not all have handsets glued to our ears. Yes, the few long-term users got more tumours “but it could be by chance”, he says.

Some might leave it there. Given the results so far, scientists could be forgiven for losing interest in the mobile phone safety debate. But Professor Challis can’t let it rest. His knowledge of the major breakthroughs in what causes cancers — smoking, sunlight, asbestos, nuclear radiation — tells him that effects often take a long time to show up. “You can look at almost any cancer where you know what the cause was. You find absolutely nothing for ten years,” he says. The groundbreaking study proving the link between lung cancer and smoking showed a similar delay, he says. “You look at what happened after the atomic bomb. Nagasaki, Hiroshima. You find again a long delay, nothing for ten years. The same for asbestos disease.” So although the many existing studies into mobile phone safety have shown no dangers does not deter him. “The people who’ve done these studies have been cautious. They say, ‘We can’t rule out the possibility’. But I want to know whether it’s there.”

As we both quietly turn off our phones, Professor Challis announced that he is in the final stages — it is hoped to seal the deal in the coming weeks — of negotiating £3.1 million from Government and industry to follow 200,000 volunteers, long-term mobile users among them, for five years. This is the kind of gold-stand-ard study he says has been lacking until now, plotting mobile use against any diseases that volunteers develop, not just cancer, but Parkinson’s and Alzheimer’s diseases and so on. He would like it to go on for ten years, to be on the safe side.

“Because there is a hint and because the professional epidemiologists whom I trust and who do this all the time, feel that there’s a chance that this could be real, they can’t rule out the possibility.”

The number of mobiles in Britain has doubled to 50 million since 2000, and the number of children aged between 5 and 9 using mobiles has increased fivefold. If, as Professor Challis fears, mobile phone risks could be slow to show up, then what about today’s children? Some scientists have said there is no cause to believe mobiles affect them in any way differently to adults.

Professor Challis disagrees. “We all know that if you’re exposed to sunlight as a kid you’re much more likely to get skin cancer than if you’re exposed as an adult. That’s why children should be covered up if you’re out in the sun all the time. We know that they react differently to ionising radiation, to radioactivity and gamma-rays. They are more sensitive to pollutants.

“Now we have absolutely no idea whether they’re different in reaction to this sort of radio frequency. But all we do know is that there are reasons why they might be. And kids are using mobile phones a lot, fortunately mostly for texting, but they’re still nattering away.”

This is why he plans a study following the fate of mobile-using children: “We want to look first at the possibilities of what are called soft outcomes. Kids’ diseases. Memory retention. These things seem highly improbable, but . . .”

His advice for now? Play safe by not giving your child a mobile before secondary school. Then encourage them to text rather than make calls.

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