To vape or not to vape: are E-cigarettes a miracle or a menace?

But there has long been uncertainty surrounding e-cigarettes. Currently used by around two million Brits, they have exploded in popularity in the past decade. Yet they are banned in some countries (it’s unlawful to sell or possess them for personal use in Australia, for example), amid widespread concern that they would have a broader appeal than merely as a tool to quit smoking, while experts remain divided about their safety. “When I started looking into it some studies suggested it was as dangerous as smoking,” Mosley says.

There are currently one billion smokers globally, and as many as half will die of smoking-related diseases. “If I was looking at the two greatest epidemics in the world today, they would be smoking and obesity. The scale of tobacco consumption and the amount of damage it’s doing is a world epidemic. People tend to think about lung cancer, but actually there’s so much else – heart disease and strokes, because basically smoking buggers up your arteries and veins. It’s the number one cause of impotence, too. Basically it hits every system in the body.”

Yet people find it hard to do what it takes to address their habit, though they know continuing can create potentially catastrophic consequences. “Just telling people to stop smoking is completely useless. It’s like telling people just to eat less,” says Mosley. “Going cold turkey is really, really hard.”

Which is where e-cigarettes come in. Inhaling them – or vaping – is a way of getting a nicotine hit without inhaling the dangerous toxins that are released in most cigarettes. But you’re still taking something into your lungs, and Mosley admits that having signed up to vape for a month he was apprehensive about the potential effects, not to mention cynical about their effectiveness as an anti-smoking tool.

“I was a bit worried that I might get addicted. I also thought inhaling something that contains a good old whack of nicotine has to be a pretty bloody awful idea. So I was quite sceptical when I went into it, but then again that’s what I love about doing these sorts of programmes.” These sorts of programmes, of course, being Mosley-as-guinea-pig, with self-experimentation a theme of much of his work.

To date, his portfolio has seen him swallow cameras to track the inner workings of the human body, ingest parasites, and try out intermittent fasting and a high intensity exercise programme (“HIT”).

The last two challenged both the way we exercise and the way we eat, suggesting that very small periods of intense exercise can be as effective as sweating it out on the treadmill and that intermittent fasting or calorie restriction can both keep us in shape and prolong life.

Making them also turned out to be life-changing for Mosley: prior to filming the Horizon documentary on intermittent fasting, he discovered he was diabetic – his own father died aged 72 of complications related to type 2 diabetes, having been diagnosed at around the same age.

His subsequent discoveries about fasting and HIT and their positive effect on blood sugar control and insulin “profoundly changed my life”, he says. Today he still has fasting days, and still incorporates HIT exercise into his daily life, convinced they are the key to longevity.

“Horizon saved my life. No male member of my family has made it beyond 72. I’m 59 now, so I have 13 years to go and I’m hoping to outdo them.”

Vaping, he believes, lies on the same narrative arc as his previous work. “I do see it as part of that journey I’ve been on,” he says. “I’m looking for other answers to big dilemmas, trying to translate what I learn into something that will actually make a difference. That’s what I’m obsessed by.”

The vaping itself left him nonplussed, more of a logistical challenge than anything, as he had to puff on one every ten minutes or so throughout the day to mimic the actions of most vapers.

“I didn’t particularly enjoy them, although I did a little bit more as I went on,” he admits. His children, meanwhile, aged 16 and 21, were “fairly underwhelmed” and apparently not tempted to ape their father. “One of the anxieties about vaping is around kids and the fact e-cigarettes are available in sweet flavours like popcorn, but when I asked my kids whether their contemporaries see vaping as cool they said not at all,” he says. “My 16-year-old thinks it’s something done by old people – old being anyone over the age of 20.”

Smoking itself, however, embraces almost every demographic: the programme follows a band of heavy smokers of all ages as they attempt to kick the habit by a variety of methods ranging from vaping and nicotine patches to cold turkey.

The results left Mosley in no doubt about the effectiveness of vaping as an anti-smoking tool, even though e-cigarettes themselves do not emerge with an entirely clean bill of health. After a month of vaping, tests on Mosley showed a slight increase in nitric oxide in his system – a marker for airway inflammation – as well as an increase in the defence cells that line the airways of the lungs to protect them from foreign bodies.

Yet for Mosley the possible side effects are “piddling” compared to the benefits. “Clearly, if you’re not a smoker than taking up vaping is a stupid thing to do, but if I was a smoker then I would certainly give it a go, despite the uncertainty.”

It’s a view shared by the Royal College of Physicians, who at the end of April published a paper suggesting that the medical establishment is swinging behind e-cigarettes, one of their conclusions being that: “provision of the nicotine that smokers are addicted to without the harmful components of tobacco smoke can prevent most of the harm from smoking”.

“I’m genuinely surprised by the fact that there’s still controversy around them,” says Mosley. “I think vaping has the potential to make a huge difference. If it even converts a small number then you are potentially talking about tens of millions of lives.”

He cites Horizon’s sound engineer, a 20-a-day, 20-year-long smoker, who took up vaping the same day as Mosley and hasn’t touched a cigarette since. “That’s a real success story right there,” he says. His own e-cigarette, meanwhile, has been consigned to history. “I gave my device away when I finished the trial and I haven’t felt a single pang for it since.”

Horizon: E-cigarettes — Miracle or Menace? airs on BBC2 tonight (Sunday 22nd May) at 9.30pm