**Core Concept**
The patient's presentation of non-productive cough, haemoptysis, grade III clubbing, and an apical lung lesion on X-ray is suggestive of a chronic and progressive lung condition that affects the upper lobe. This is a classic presentation of a condition that involves the destruction of lung tissue and the formation of cavities.

**Why the Correct Answer is Right**
The most likely diagnosis here is pulmonary tuberculosis (TB), a bacterial infection caused by Mycobacterium tuberculosis. The patient's symptoms, such as non-productive cough, haemoptysis, and clubbing, are consistent with pulmonary TB. The apical location of the lesion is also characteristic of TB, which often affects the upper lobes of the lungs. The destruction of lung tissue and the formation of cavities are hallmarks of TB, which can lead to the characteristic symptoms and radiographic findings in this patient.

**Why Each Wrong Option is Incorrect**
* **Option A:** While lung cancer can present with similar symptoms, it is less likely to cause clubbing and is more commonly associated with a central or hilar mass rather than an apical lesion.
* **Option B:** Bronchiectasis can cause chronic cough and haemoptysis, but it is typically associated with a more diffuse pattern of lung involvement rather than a focal lesion in the apical lobe.
* **Option C:** Pulmonary embolism can cause acute onset of cough and haemoptysis, but it is unlikely to cause chronic symptoms or clubbing.

**Clinical Pearl / High-Yield Fact**
The "Pott's triad" is a classic presentation of pulmonary TB, consisting of cough, haemoptysis, and clubbing. This triad is often seen in patients with chronic and progressive pulmonary TB.

**Correct Answer:** C.