James Thomlinson has had lung problems all his life.
They began when he was born prematurely by emergency caesarean and needed oxygen.
At four, he suffered from whooping cough He was diagnosed with pneumonia for the first time at seven.
Since then, he has had frequent chest infections including croup and chronic bronchitis - and at least 10 bouts of pneumonia.
Doctors assumed he had asthma.
It was not until he was at university that a barrage of tests revealed he had severe scarring on one lung and the lung conditions bronchiectasis and emphysema - a disease usually associated with people much older.
Both come under the umbrella term chronic obstructive pulmonary disease (COPD) the collective term for a group of lung diseases that make breathing difficult.
He also has an antibody deficiency that means his body cannot fight the chest-infections properly.
"COPD is very much associated with old people, smokers or people who have worked in polluted areas but that is not the case at all."
James is angry that it took so long to diagnose his condition accurately. He says knowing sooner would have enabled him to work on protecting his lungs earlier.
"Not enough people are aware of COPD and it is important to create awareness of this terrible disease.
"It is incredibly important to diagnose people with lung disease at an early stage and I feel that had this happened to me, the time when my lung was deteriorating could have been significantly reduced.
When well, James tries to keep as fit as possible.
"I take great care with my diet," he said. "I make sure that I do physio and breathing as often as I can.
James works full-time, plays football and ran the London Marathon for the British Lung Foundation in 2007.
Professor Sue Hill, chief scientific officer and joint national clinical director for respiratory disease at the Department of Health, said the simple spirometry (lung function) test was vital.
"In this country it is a tragedy that most people with COPD and other lung conditions are not diagnosed until they have lost over half of their lung function," she said.
"Unlike other parts of the body, lung damage cannot be repaired."
Dame Helena Shovelton, chief executive of the British Lung Foundation agreed: "Research has shown that there are currently over 2.8m people in the UK who are living with COPD but don't know it.
"This is why we are encouraging those with symptoms such as a persistent cough with phlegm, breathlessness or a wheezy chest to visit their GP for a lung function test.
"Early diagnosis is essential to slow the progression of COPD to ensure that those with the disease can manage their condition properly and live with COPD rather than suffering in silence with an invisible disease".
Professor Mike Morgan said the numbers with the condition were probably much higher than suspected.
"We know that probably as many as four times as many people have COPD than have been identified by GPs.
"It is a much more common than realised. This is a condition which can also affect younger people.
"What is important to realise is that the lung as an organ is easily influenced by early life events.
"If your lungs are damaged by the age of four the chances are you will not attain your peak lung function, which is achieved at 25 thereafter what you have got lasts your life.
"Patients like James can compensate for a lack of lung function by remaining fit."
But he added: "If your lungs are suboptimal at 25 they will stay that way."