'That incident happened in the middle of my tour and after that I thought nobody can kill us now - when we met the enemy I wasn't scared.
'I thought the Taliban did not have the capacity to fight with us.'
Cpl Pun, an acting sergeant during his Afghan deployment, was on sentry duty at the time of the attack when he heard a clinking noise outside the small base.
At first he thought it might be a donkey or a cow, but when he went to investigate he found two insurgents digging a trench to lay an improvised explosive device (IED) at the checkpoint's front gate.
He realised that he was completely surrounded and that the Taliban were about to launch a well-planned attempt to overrun the compound.
The enemy opened fire from all sides, destroying the sentry position where the soldier had been on duty minutes before.
Defending the base from the roof, the Gurkha remained under continuous attack from rocket-propelled grenades and AK47s for more than a quarter of an hour.
Most of the militants were about 50ft away from him, but at one point he turned around to see a 'huge' Taliban fighter looming over him.
The soldier picked up his machine gun and fired a long burst at the man until he fell off the roof.
When another insurgent tried to climb up to his position, the Gurkha attempted to shoot him with his SA80 rifle. But it did not work, either because it had jammed or because the magazine was empty.
He first grabbed a sandbag but it had not been tied up and the contents fell to the floor.
Then he seized the metal tripod of his machine gun and threw it at the approaching Taliban militant, shouting in Nepali 'Marchu talai' ('I will kill you') and knocking him down.
Two insurgents were still attacking by the time the heroic Gurkha had used up all his ammunition, but he set off a Claymore mine to repel them.
At this point his company commander, Major Shaun Chandler, arrived at the checkpoint, slapped him on the back and asked if he was OK.
In total he fired off 250 general purpose machine gun rounds, 180 SA80 rounds, six phosphorous grenades, six normal grenades, five underslung grenade launcher rounds and one Claymore mine.
The only weapon he did not use was the traditional Kukri knife carried by Gurkhas because he did not have his with him at the time.
These guys always amaze me.