David Cameron never felt that he needed to apologise for having been educated at Eton, but he did – in that conference speech – feel that he needed to explain. His alma mater is one of our most privileged seats of learning and, although most of us have no connection with it, we all think we know what it’s like. We think we know about the people it produces, too – posh, grand types with an innate sense of entitlement.

Such assumptions may be based on generalisations but, in one sense, Eton has only itself to blame. Outsiders are often kept at arm’s length. I was astonished to learn that, over the past 40 years, the school has granted access for the making of TV documentaries only three times. Later this month, however, a new film for Channel 4 gives us a fresh glimpse of its inner workings.

A Boy Called Alex, the first in this season’s acclaimed Cutting Edge strand, tells the story of Alex Stobbs, who, at 17, is one of Eton’s foremost music scholars. As a pianist and chorister, Alex has been winning prizes most of his life. His prodigious talents have taken him on tours to Europe, the US and Australia, and he has performed for the Queen.

Alex’s father Tim works in reinsurance and his mother Suzanne is a piano teacher. Actually, Suzanne is my son’s piano teacher, so I can vouch that they are neither posh nor grand. Eton pays their son’s fees in full (a scholarship covers 50 per cent, with means-tested assistance making up the balance), enabling Alex to cultivate his genius in a music department that can boast the expert tuition of 70 specialist teachers.

But there is something else that makes Alex’s story truly remarkable. He has cystic fibrosis, the degenerative disease that clogs the lungs and pancreas with mucus and could, at any moment, cut short his life.

CF is an inherited disease caused by a recessive gene, but in Alex’s case there were no clues in the family history. One person in 25 is a carrier, but until Alex – the youngest child of four – was born, neither Suzanne nor Tim knew of the risk.

His diagnosis, at seven weeks old, signalled the start of a relentless care regimen that continues to this day. He takes about 50 tablets each day, plus several syringes of antibiot-ics that are pumped into his blood-stream through a porta-cath – an implanted intravenous device. He needs three physiotherapy sessions a day to clear his chest of the mucus build-up, as well as oxygen and a food supplement, fed through a gastric tube, to get him through the night. At Eton his care is managed by a part-time nurse, paid for by the school. His room contains the medical equipment that he tries to keep hidden from others. “People act differently when they know, so I only tell them so much,” he says.

Like any teenager, he just wants to fit in – and when we meet, it is clear that he does. In his tailcoat and winged collar, he looks like any other Eton boy. He is engaging, funny and relentlessly determined. Stamina is his main problem, but again Eton has come to his rescue, permitting him to use a shiny silver electric scooter. Skimming over the cobblestones, he takes me across School Yard, the austere Gothic square, and then to the 15th-century chapel, where he plays Chopin’s Grand Polonaise on the piano and, despite the midwinter chill, I find myself melting on the spot.

All the Stobbs children have been musical scholars “but Alex has that special something”, says Suzanne. For him, music was a joyous relief from the incessant hospital visits that punctuated his early childhood.

He could play piano by ear from the age of 3, won a prep school scholarship at 6 and became a King’s chorister at 9 – an accomplishment that set him on a fast track to Eton, but also meant him leaving the family home in Kent to be a boarder in Cambridge, where his care was managed by a “fantastic” team of matrons. “Everyone has worked so hard to give him a chance,” says Suzanne.

The Channel 4 documentary stems from a chance conversation 18 months ago between Stephen Walker, the award-winning film-maker, and Ralph Allwood, Eton’s precentor and director of music. Both confess to usually blanking the stranger seated next to them on flights but, en route to New York, they struck up a rapport. “Somewhere above Greenland he told me about Alex,” Walker recalls, “and once we had started talking about him, we didn’t stop.”

Walker follows Alex over seven weeks as he prepares to conduct the Bach Magnificat – a hugely complex masterpiece in 12 movements. Alex assembles the required 62 musicians and coordinates hours of rehearsals, only to be taken critically ill midway through his preparations.

Such hiccups are part of the fabric of his life. “Infections come out of nowhere,” he shrugs. In his five years at Eton, he has never completed a full term without being admitted to the Royal Brompton Hospital in London, where he stays for up to three weeks at a time while antibiotics are pumped into his system. Because of this disruption he has yet to take any GCSEs, although he is now working towards English and maths alongside music and history A levels. A more devastating consequence of his illness is that the drugs have left him partially deaf and unable to hear the very top notes of the music that he plays.

Alex’s instinct, when talking about his CF, is to play it down, but his mother points out that when a serious infection takes hold, there is always a danger that he won’t pull through. “He could have a sudden lung collapse and die,” she says. “We are aware of that. It is unpredictable and dangerous.”

The infection that he finds himself fighting during filming of the documentary reduces his lung capacity to 29 per cent – a level that, without improvement, would give him no more than a 50-50 chance of surviving the next two years. It has climbed back since: on a good day it is above 40 per cent. But in the longer term he may have to consider a lung transplant, which carries huge risks. Only half of those who have the operation survive beyond five years. It is not a subject on which Alex likes to dwell: “I haven’t got my head in the sand. It’s just that those aren’t the sort of questions I need to answer right now.”

For the most part, Alex lives resolutely in the moment, and being able to immerse himself in music at Eton makes that task all the sweeter. “His world is not about having CF and managing that. It is about his music,” says Suzanne. This summer Alex will leave Eton, hopefully for Cambridge, where he has the conditional offer of a choral scholarship from King’s College.

Ralph Allwood has been teaching at Eton for 20 years. As a former grammar school boy, he is aware of the school’s reputation for producing arrogant young men. But the privilege, for music scholars at least, he says, is that the place is so awash with talent “that the arrogance factor happens in the opposite direction. If Alex went elsewhere, he might think he was God’s gift to music. Here he is just part of the team”.

Well, almost. Eton has produced many great musicians but never one with CF. So has Alex taught Eton something? Allwood directs his answer to Alex rather than me. “We see you getting on with your life with real joy and if something goes wrong for us we can see that, in comparison, it’s trivial. You are a great example to the boys, the rest of the staff and me. If we don’t articulate it, that’s only because it’s obvious.”

— A Boy Called Alex, Cutting Edge, Channel 4, January 24, 9pm

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