Mr Parker is a 62 year old new patient to your GP surgery and attends for his new patient review appointment. He has never smoked, drinks 3 units of alcohol a week and his weight is stable. He says over the last 6 months he has become more chesty and has a frequent productive cough. On a few occasions he has noted a little haemoptysis but denies any shortness of breath.
On examination you hear coarse crackles bilaterally in the lower lung fields.
What is the most likely diagnosis?