To Michael, medical science wasn't something just for the chosen few - he was passionate about making sure everyone could understand it. That's why people told him every day how he had affected their lives, writes co-star SALEYHA AHSAN

Michael Mosley taught me how to be a TV presenter. He was my mentor, from the first time I met him, a dozen years ago. I learnt from the best.

But in spite of his immense experience, he always seemed to be an eternal schoolboy. His bottomless enthusiasm, his little bit of cheekiness and touch of shyness gave him a youthful air that was completely charming. He had a genuine smile and glint in his eye whenever science was on the agenda.

Everyone loved him – colleagues, the scientists and fellow doctors he interviewed, and members of the public. Yet he remained essentially modest, a down-to-earth guy, and though people told him every day how he had affected their lives in so many positive ways, I wonder if he realised how very much loved he was.

The outpouring of concern and affection for him this week has been deeply touching to me and colleagues, and I hope it has been a source of comfort to his family, to the extent that anything can be. He would be amazed by the reaction in Britain and abroad, by the genuine sense of shock his disappearance provoked, and by the grief that greeted news today that his body had been discovered.

In my experience, plenty of people in television are just like their on-screen persona, but none more so than Michael. I first worked with him in about 2012, when I auditioned for Trust Me, I'm A Doctor, the BBC2 medical magazine show he both fronted and helped to produce.

For my screen test, we filmed a chat together, to help the director gauge what sort of rapport we projected. Though I had been nervous before arriving at the studio, Michael put me at ease almost as soon as we were introduced.

He was so engaging, so entertaining, that I ceased to notice the cameras and the lights, and became absorbed in our discussion. I have no doubt that's what enabled me to land the job, and I've sometimes reflected that, if the presenter had been anybody else, I might not have been hired. Just through that first meeting, Michael had a significant impact on my life, as on so many others.

Whenever I watched him on TV, I had the feeling that it was just the two of us, sharing an entertaining conversation. I'm sure millions of other people had exactly the same experience. It's a rare gift, and one that is entirely instinctive: he never seemed to be performing for a camera, and he always had so much to say.

I remember watching how he prepared for his pieces to camera, with such confidence. I adopted his approach and didn't feel self-conscious any more.

To Michael, medical science wasn't something just for the chosen few. He was passionate about making sure everyone could understand it, because anything that affects our health is equally important for all.

That was true not only of intermittent fasting and the 5:2 diet for which he was best-known, but for the benefits of meditation, the physiological effects of cold water swimming and many other topics.

A few years ago I was making a documentary about Ramadan and he had agreed for me to interview him about intermittent fasting.

It happened that the Muslim holy month fell during the summer that year, which meant the daylight hours of fasting would be particularly long and hot.

After we finished filming, Michael took the time to ask whether I was OK. I told him I was worried about it. Then he gave me some reassuring advice I've never forgotten: 'Being hungry is hormonal. When your stomach gets empty, it releases a hormone called ghrelin, and that's what triggers the brain. It sends a message to say, 'Fill me now!' You can do this.'

That piece of knowledge has proved mentally powerful for me during every Ramadan since. I can literally hear his words. I no longer think about 'being hungry' – I just note that my gut is producing plenty of ghrelin. I'm not really starving, it's merely a hormone.

Michael had time for everyone in that way. When we did live events for the Cheltenham Science Festival, the auditorium would always be packed. And then afterwards, so many people wanted to meet him, and he was so generous with his time and attention.

People were especially inspired, I realised, by the fact that he used his own life as the basis for his research. He wasn't preaching, or laying down rules for others to follow. He was sharing his own experiences, especially his success in pulling his body back from the brink of Type 2 diabetes.

All through the past few days of gnawing anxiety, I felt sure he would somehow come through alive.

His death will leave a huge hole, not only in the lives of those who knew him personally but in the world of television. There's never been anyone like Dr Michael Mosley. He'll be irreplaceable.

Dr Saleyha Ahsan is a co-presenter of Michael Mosley's Trust Me, I'm A Doctor.