**Core Concept**
Papilloedema is a condition characterized by swelling of the optic disc due to increased intracranial pressure. The development of papilloedema depends on several factors, but the most critical factor is the rate at which intracranial pressure increases.

**Why the Correct Answer is Right**
The rate of increase in intracranial pressure is the most crucial factor in the development of papilloedema. This is because the optic nerve sheath is sensitive to changes in intracranial pressure, and rapid increases in pressure can lead to compression of the optic nerve, resulting in papilloedema. The optic nerve sheath is surrounded by cerebrospinal fluid, and any increase in intracranial pressure can cause the cerebrospinal fluid to compress the optic nerve, leading to papilloedema.

**Why Each Wrong Option is Incorrect**
**Option A:** The size of the intracranial tumour is not the most important factor in the development of papilloedema. While large tumours can cause increased intracranial pressure, smaller tumours can also cause papilloedema if they are located in a critical area of the brain.
**Option B:** The location of the intracranial tumour is not the most important factor in the development of papilloedema. Tumours located in different areas of the brain can cause increased intracranial pressure, leading to papilloedema.
**Option C:** The type of intracranial tumour is not the most important factor in the development of papilloedema. Different types of tumours can cause increased intracranial pressure, leading to papilloedema.

**Clinical Pearl / High-Yield Fact**
The rate of increase in intracranial pressure is the most critical factor in the development of papilloedema. This is why patients with rapidly increasing intracranial pressure are at higher risk of developing papilloedema. A mnemonic to remember this is "RAPID": Rate of increase, Age, Pressure, Intracranial disease.

**Correct Answer:** C.