A sigh, or a yawn. A great, big, chest-expanding, lungs-full- to-burst gulp of air.
The simple pleasure of taking a deep, satisfying breath is something most of us would find fairly unremarkable.
For Anthony Usher, however, doing so represents something near miraculous.
The 31-year-old from Liverpool has cystic fibrosis, an incurable genetic condition that destroys the lungs and digestive system.
The disease has already claimed the life of his identical twin, Elliott, who died late last year.
Anthony, who described his brother simply as 'my best mate… my other half', was with him at the end.
'I held his hand and stroked his hair,' he said. 'I wanted to make sure he was comforted, and that he didn't feel alone.'
Cystic fibrosis sufferer Anthony Usher, above, says his lungs were transformed by Kaftrio within hours of taking it
When we first spoke in June, Anthony was still reeling from the loss – and fighting to regain his own health, on the very same ward at Broadgreen Hospital where Elliott died.
Infection after infection had ravaged Anthony's body. Powerful medicines used to control the illness had given him diabetes and his lung function hovered at about 50 per cent, leaving him fighting for every breath.
Our conversations would be punctuated by short coughing fits – and he told me that, in his darkest moments, he would wake in the night, gripped with anxiety about his uncertain future.
When he answers the telephone today, the contrast is immediately obvious. His voice is stronger. There's no coughing.
'I can breathe again,' he tells me, taking an audible, deep breath to demonstrate. This turnaround is thanks to Kaftrio, a medication for cystic fibrosis which is having astonishing effects.
The drug was given the NHS stamp of approval last summer – following months of deadlocked talks – and Anthony is among the first British patients to take it.
As first reported in The Mail on Sunday in June, the £1 billion deal for the medication is one of the biggest in NHS history.
Recalling the moment he heard the news, Anthony says: 'I was with my partner Kathryn. We just cried with happiness, and then I called my mum and she cried her eyes out too.
'All of my family were waiting for this. Losing our Elli, it had been a bad year, and this gave us such a lift. I'd been feeling so defeated – my mood was really low. I wasn't the same person. I had been in and out of hospital and doctors didn't know what to do. It was scary.
'To know I'd get a drug that would finally help me was a weight off all of our shoulders.'
Kaftrio's approval was a watershed moment, and one that marked the end of months of uncertainty – time that people with cystic fibrosis, such as Anthony, could ill afford.
The condition, which most patients are diagnosed with as babies, kills the majority of sufferers before middle age. For them, every day counts.
Pictured: An old photo of Anthony, left, aged 16, with his twin Elliott, who died last year
And yet, as this newspaper had exclusively revealed, an ongoing row between NHS England financial chiefs and drug company bosses over the price of Kaftrio meant the deal, on a number of occasions, came close to collapse.
Over the past year, the MoS published a series of reports, lifting the lid on the secretive negotiations.
Last November, we revealed how the NHS had agreed to spend £100 million on older cystic fibrosis drug Orkambi – and announced the deal just days after the newer, vastly more effective Kaftrio was approved for patients in America.
While Orkambi could, in some cases, hold the disease at bay, it was effective in less than 45 per cent of patients.
But Kaftrio – priced on its own at £28,000 per patient per year – works for 90 per cent of those with cystic fibrosis. It has been dubbed the holy grail of treatments by sufferers, and brings about an incredible transformation, boosting lung function dramatically.
It effectively rendered the older drugs obsolete – not that any of this was mentioned when the NHS contract for Orkambi was announced.
At the time, Secretary of State for Health, Matt Hancock, took to the airwaves claiming their deal was 'the best in the world… and another reason to be so proud of our NHS'. But insiders told us a different story.
Politicians were desperate for positive news as a General Election loomed, yet were unwilling to pay what drug-maker Vertex was asking for Kaftrio.
And so they 'fudged' a deal that would give patients the outdated Orkambi while specifically excluding any agreement for Kaftrio.
Our revelations put pressure on NHS deal-makers and had them heading back to the negotiating table.
And finally, after further tense talks, in July came relief – the old deal was scrapped, and a new agreement that included Kaftrio was struck.
CYSTIC FIBROSIS FACT
In the 1950s, people with the condition often died in childhood.
Now they’re expected to live into their 60s and beyond.
Now the majority of Britain's 10,000 cystic fibrosis patients can truly plan for a future – one less blighted by hospital visits, endless rounds of antibiotics and other powerful drugs that cause horrific side effects.
And also a future less overshadowed by the threat of Covid-19. The infection is thought to be particularly severe for those with illnesses that affect breathing. Kaftrio brings about a dramatic improvement in lung function, which should theoretically give patients more of a fighting chance against the virus.
Anthony, who lives with partner Kathryn, 30, a civil engineer, received his first packs of Kaftrio three weeks ago by post, and began taking the pills immediately.
'Within a few hours of the first dose, I felt different,' he says.
Cystic fibrosis causes a wide range of symptoms, but patients usually develop thick sticky mucus in the lungs, digestive system and other organs. In the lungs, in particular, this increases the risk of infections, and patients can become severely unwell from a simple cold.
A large part of managing the disease involves taking medications to help loosen mucus in the airways, alongside physiotherapy exercises aimed at helping cough it up.
Kaftrio works by correcting the fault in cells that causes the thick mucus, making it thin out and more like the mucus in a healthy person. The effect is dramatic.
'I immediately started coughing up phlegm – normally it's a struggle, and I go red in the face, but it was really loose and seemed to be coming out of its own accord,' says Anthony.
'This just carried on all day, and then all night – people with cystic fibrosis who take the drug are calling it 'the purge'. I was bringing up stuff that had been down there for a while. Now I don't really cough, and when I do it's just like I'm clearing my throat.
'I used to be so loud when I coughed, I'd make Kathryn jump.'
He has already begun to reduce or stop taking other medications he's on – including the one that triggered his diabetes. And, most remarkably, Anthony's lung function has leapt to 72 per cent.
'It's not been this good since 2016,' he adds. 'To be honest, it's hard to get my head round it. I used to wake up coughing all night, but now I'm sleeping better and I wake up with energy. It's not a cure, but I feel like my body has been rewound.
'I feel the same as I did when I was 25. I feel like a normal person. My panic attacks have stopped. I've even been able to go jogging.'
He takes another deep breath.
'When I tried to breathe in before, it was like someone was squeezing my chest, stopping me. That's gone.'
I also speak to 29-year-old Laura Gayton, another cystic fibrosis patient whose story we featured earlier this year.
She had been shielding since the start of the pandemic. With her lung function deteriorating rapidly, an illness such as Covid-19 could be catastrophic.
Last time I heard from her, she'd just returned home from hospital where she was having treatment for a persistent lung infection.
Laura, who lives with firefighter husband Nicholas, 32, started on Kaftrio a month ago, and within a week her lung function had leapt from about 55 per cent to 81 per cent.
'Before this, I was in hospital up to eight times a year,' she says. 'The last time I saw my consultant, a few weeks back, she joked that I wouldn't need to come back for six years.
'I'm turning 30 in November, and they said I'd never live this long. I feel a bit tired, which I was warned would be a side effect, but I can breathe. It's incredible that three pills a day can do this.'
And when we last heard from cystic fibrosis sufferer Tim Wotton, 49, he had just returned to his London home, in early August, after moving to Southampton to shield with his retired nurse mother.
The father-of-one lived there for more than four months.Tim, who started on Kaftrio at the start of September, says he began to feel the effects just 20 minutes after taking his first tablets.
He says: 'At my age, I live with lots of lung damage – my best days were most healthy people's worst days.
'The first week or so were difficult, as I was constantly coughing up phlegm, even at night. But now I'm hardly producing any mucus, which is a revelation.
'Before, I'd cough for the first two hours of the day like a 40-a-day smoker, despite the fact I've never touched a cigarette. Now I've been able to run further and push myself more in the gym.
I feel like I'm getting fitter. Earlier this month, my 13-year-old son Felix came back from school with a cold, and I caught it.
'We had Covid tests, and quarantined until they came back negative. I had a fever, but recovered remarkably quickly. And now I feel back to normal again.
'It feels like Kaftrio has given me some armour plating.'
Anthony Usher admits he can't shake the feeling that it's all too good to be true. 'It's scary. I've lived with this worry hanging over my head,' he says.
'I keep thinking, where's the catch? I'm trying not to dwell on that, and just enjoy it. Kathryn and I are making plans. We want to go on holiday. Maybe we'll try for a family. Before, it felt like that was out of the question, but now…'
He also can't help thinking of Elliott. 'I just wish he could have had this. And all the others who died. They might still be here.'
On Kathryn's birthday last month, the couple and a few friends went to the Otterspool Promenade, a spot overlooking the Mersey that Elliott loved – and released balloons in his memory.
'We'd go to the Prom as kids, and sit and watch the planes go past, and talk for hours about what I don't know,' says Anthony.
'When we released the balloons, we thought they'd float off into the distance over the river, but the wind blew them back on to the grass behind us, and we had to chase them. I know if Elli had been there, he'd have been crying his eyes out laughing.
'Everything seems overwhelming at the moment. But I'll be forever grateful for this drug. It's a turning point. I'm on a high. I feel like I've got my life ahead of me.'