His comedy routine was brilliant - fast, funny and very physical - and Bill Bailey had the audience roaring with laughter at the Riverside Studios in London. Then, suddenly, he shouted out, 'I'm having an asthma attack!' And with that, the comic ran off stage, leaving the audience still laughing.
What they did not know was that Bill was desperately struggling to breathe and had fled to his dressing room in search of an inhaler.
'It was one of those very weird moments,' says Bill, 45. 'I had not brought the inhaler on stage with me because it is bulky and shows in your pocket, but I was feeling stressed because I was preparing to embark on my first tour of large international arenas.
No laughing matter: Bill Bailey has missed out on lots of sports thanks to his asthma
'I sometimes introduce spontaneous physicality into my routine and I found myself leaping about the stage and noticed I was starting to wheeze.'
Thankfully, his medication soothed his airways and he was able to return to the stage and finish his routine.
'After that I decided enough was enough. I couldn't run the risk of that happening again on tour, so I saw my GP and was referred to a specialist at St Thomas' Hospital in London. He ran some tests and concluded my lung capacity was quite low and he put me on different medication.
'That was in 2007 and I haven't looked back since. Changing the medication has lifted a huge burden of worry from my shoulders. I haven't wheezed or felt any tightness across my chest since I started using it, and now if I ever need to run to catch a taxi or jump on my bike, I can be sure I will be fine.'
Asthma is a condition that Bill has lived with since a child - when, terrifyingly, he once almost drowned during an attack. On one hot day during a school summer language trip to Austria, Bill - then 16 - joined in with friends diving into a lake and attempting to swim across to the other side. But Bill ran into trouble when only half-way across.
'I suddenly felt that familiar feeling of tightness in my chest and realised, with horror, that I wasn't able to catch enough breath,' he says.
'It's terrifying when it happens because you feel you can't get enough breath in, nor expel enough to shout for help, so I started to flounder around and then I went under.
'I swallowed water and started to panic, but thankfully a few of my friends noticed that I was in trouble and swam over to help me to shore.
'I remember lying on my side spluttering and coughing - it put a real fear of deep water in my mind and for years afterwards I would avoid swimming except in indoor pools
Joker: Bill Bailey during his stand-up routine
But, serious as it has been for him, Bill has not been able to resist poking fun at the condition in his routines. 'I was touring Australia, where they have a high incidence,' he says, when we meet in a pub near his home in Hammersmith, West London.
'And America gets it badly too. But in the undeveloped countries there is more smog, smoke and pollution but less asthma, so the conclusion I drew was it somehow must be triggered by our common language.
'I'd seriously like to know what causes it because I have found asthma can be very debilitating. Until I changed medication two years ago, I was getting very worried about having attacks and I always avoided unplanned physical activity just in case I finished up not being able to breathe properly. It felt like living with a constant threat.'
Asthma, an inflammation of the bronchial tubes, affects one in ten children in the UK and one in 20 adults. There are 5.5 million adults being treated for it in the UK.
The precise causes are unknown, but when small tubes in the lung become inflamed, it irritates the surrounding muscles, which constrict and narrow the airways, and at the same time excess mucus clogs the tube lining, further reducing air capacity.
The condition can be triggered by physical activity, infections, allergic reactions, smoke, fumes and stress. Symptoms range from a tightness across the chest, to wheezing, coughing and struggling to catch breath - asthma sufferers frequently report a 'rattling' sound on the intake of breath as air passes over excess mucus.
Until two years ago, Bill thought he had his asthma under control using inhalers.
He made his name as Manny in the Channel 4 comedy series Black Books, opposite Simon Pegg, whom he would go on to work with in the British comedy film, Hot Fuzz.
As one of Britain's most popular comics, he was team captain on BBC2's quiz show Never Mind The Buzzcocks, and he frequently appears with Stephen Fry on the BBC quiz QI, as well as touring with his stand-up comedy routine.
He says he leads a fairly 'normal' life in Hammersmith where he lives with his wife Kristin, 46, and their son Dax, six.
Their son does not show any signs of developing the condition, which Bill says he remembers discovering at the age of 11 after running around in the back garden at his parents' home in Keynsham near Bristol.
TV success: Bill Bailey with Tamsin Grieg, Dylan Moran and, right, Simon Pegg in the series Black Books
Experiencing for the first time the 'rattling' and wheezing that has since become familiar to him, Bill was fortunate to be able to go to his father, Christopher, a GP, who quickly diagnosed the onset of asthma.
'I'm an only child and neither of my parents had asthma. But my father diagnosed me - and he initially prescribed tablets, which brought the wheezing under control within about half an hour. He told me to take the tablets whenever I felt any symptoms, but within a year I switched to an inhaler which was becoming more commonly used to treat asthma.'
Over the next five years, Bill used two inhalers, a steroid called Becotide to prevent inflammation, and Ventolin to relieve symptoms if the condition were triggered.
He could play football at school and participate in games, but he quickly discovered breathing afterwards would be easier if he warmed up first.
'Classic asthma can be relatively easy to diagnose,' says Dr Michael Thomas, chief medical advisor to Asthma UK. 'But it can also be present intermittently and many of the tests we use are quite crude, so in some cases it can be hard to spot.
'Asthma is now understood to be a quite complex condition resulting from a mix of genetic and environmental 'One possible explanation is the hygiene hypothesis - that we are now all so clean we don't expose our children to enough germs and infection to prepare their immune systems against allergic reaction. But there is also a genetic element, so if parents have it, a child is more likely to develop it.'
Around half the children who suffer with asthma will grow out of the condition.
Indeed, Bill began to wonder whether his condition was improving in his 20s. Although he kept inhalers around the house and in the glove box of his car, he found he was using them less frequently.
However, there were still certain triggers that he had to remain wary of. Cold starts to the day might set him off, for example, and he would avoid unplanned physical exertion, so if he ever had to catch a bus or was late for a meeting he would never run.
'Most of the time I saw my asthma as a mere annoyance,' says Bill. 'But I felt constricted by it because it meant there were things I couldn't do easily, like join a five-a-side football game, jump on my bike, or go skiing. And then when stress brought it all on again two years ago, I started to get really worried.'
The specialist at St Thomas' Hospital prescribed a drug called Symbicort, a mixture of preventative steroid and muscle relaxant, inhaled in powder form. Bill now uses that twice a day at morning and at night and has so far not needed to use any separate reliever.
Although now due to make a return appointment at the hospital to monitor his condition and usage, Bill has seen a big improvement. He regularly has medical examinations for his TV work and has noticed in 'peak flow' tests, which involve blowing into a tube to measure constriction in the airways, that his readings indicate his lungs have already improved by a factor of two.
Dr Thomas was not surprised to learn that changing Bill's treatment was so effective, but he warns that although asthma is extremely common, each patient needs individual assessment.
'Ten years ago, the standard treatment was two separate inhalers,' says Dr Thomas, 'but more recently, patients have been given compound inhalers which combine the two and Bill now uses one, which has been a real step forward.
'Many patients report that it has brought their asthma under greater control, but there are now a range of different treatments available and it's important to see a specialist for individual advice.'
Bill says: 'I was a bit cross at the time to discover I had been using a medication that was not as effective but I'm pleased to have it all under control.
'It was becoming a vicious cycle - sometimes the fear of having an asthma attack or leaving the house without my inhaler would actually bring it on. But now I'm generally far more relaxed.'