I’m not a morning person, but here in Helmand province it always starts early. I sleep on top of my vehicle: a 23-tonne Mastiff armoured personnel carrier. I never sleep deeply: I half-listen to the radios chirping in my ear as I lie under the most intense stars. I’m up before the sun, as soldiers have done throughout history.

There are five of us who live and fight on my vehicle. Our morning routine is efficient: sleeping bags are packed away, weapons checked, the petrol cooker is lit in the foot well of the vehicle. Breakfast is a hurried affair. The others can’t operate in the morning without food and I can’t operate without coffee. So I’m normally grumpy as I watch the boiling water heat everyone else’s food and impatiently wait to pour the water into my mug. I will grab a chocolate bar later.

By first light, 6.30 in the winter, the squadron is ready to move. I normally bring in my officers and sergeants for an update about what we’re doing that day, and we’re off. During a six-month tour in Afghanistan there’s been much variety, from the intensity of fighting to recapture Musa Qal’eh from the Taliban, to delivering aid to mountain villages.

No day is ever the same. We might be supporting the Afghan government’s counter-narcotics efforts, raiding a drugs laboratory that nestles on the side of the Helmand River. B Squadron will deliver an Afghan army unit to the lab and provide them with protection; they will search the lab and take evidence. In a typical lab there may be over a tonne of unrefined opiate paste and 100 kilos of refined heroin powder. The Afghans will take samples of the drugs for forensic evidential purposes and the rest is destroyed through controlled explosions.

In our last raid the Scots Guards secured our line of departure, the point from which we launch forward onto the lab. As I follow down the track, I scan the compound walls on either side. One or two well-placed Taliban fighters could cause us problems. I load a round into the breech of my carbine and select automatic. Five-hundred metres further and we’re at the track junction identified from aerial photos. I double-check my GPS and give the order for the Afghan soldiers to “debus”. Once they’re on the ground, B Squadron establishes a protective screen around the lab. The Afghans move quickly, seizing an entry point into the drugs lab. After 60 minutes their commander reports that the lab is rigged for explosion and that they are ready to leave the area.

“Fifteen seconds — take cover!” The shock wave is predictable as a black cloud rises into the air, signalling that the heroin and its production equipment have been vaporised by the plastic explosives. The Afghan soldiers climb back into my vehicles and we move out, into the relative security of the desert.

By lunch time the heat from the sun is intense and I find cover among the hills above the Helmand River. We get the cookers out to make tea. As we settle down for lunch, vehicle gunners scan the horizon, watching for Taliban spotters who may try to attack. After 30 minutes we will move again.

I have been in the army for the last 14 years, but this tour in Afghanistan has been the most demanding — and the most rewarding — I’ve been on. My soldiers revel in the fact that every day they’re making a small difference to both the Afghan population and to the wider international community. Reducing the quantity of heroin making its way onto the streets of western Europe may have tangible benefit, but seeing children being able to go to school for the first time in 10 years was a poignant moment for me. Education had been banned under the Taliban: those children that did go to school had their throats cut. With the Taliban ousted from Musa Qal’eh and with the Afghan army and police now back on the streets, the first school has been reopened.

By 17.30 I try to have the squadron established in a “lying up” position for the night, tucked away in a valley. We will cook before the light fades. Army rations have come a long way over the last few years; now everything is “boil in the bag” — one per man. Light the stove, boil a litre of water, and throw the bags in for all of the crew. Five minutes later you are eating lamb curry, tuna rigatoni or beef ravioli. They are good, and while there are 25 different menus, on the 140th day of eating boil in the bag there is only a certain amount of enthusiasm you can muster for chicken with herb dumplings. We tend to perk them up a bit with Tabasco, chilli or ketchup.

Before going to bed I type up my daily report and dispatch it by satellite. As the sun goes down we whisper and keep torch light to a minimum: it’s not uncommon for the Taliban to drive into the desert at night looking for us. Twice a week I will try to phone Jules on the satellite phone. We won’t talk about my work — she’d rather not be reminded of the dangers — so she keeps me amused with the daily antics of our two young girls. Maisie has taken her first steps since I’ve been away, and although Scarlett is only two, she appears to be missing me far more than we’d anticipated. As I get into my sleeping bag I’ll lay out my carbine and night-vision goggles onto the roof of the vehicle, then I settle down, tuning my ear into the sounds of the Afghan night.

By Major Richard Slack

Times recommends

• The pink mile: women on death row
• The top 10 richest streets in the world
• Japan's new professional seducers