My core temperature has fallen two degrees, which means I'm hypothermic. My muscles are stiffening and my brain is cooling. If I lose my wits, I have no chance. Even shivering stops as the muscles slow down. Now a little test. Count down from a hundred, taking seven away each time. A hundred minus seven. Hundred minus seven, OK. Hundred minus seven, ninety three. Minus seven? Er... Eighty... hundred minus... Eighty six. I feel I've got the flu, I've a headache. As the vital organs cool, the body starts to shut down. This is the critical stage. Then he would become tired and would like a little sleep, but to survive you've to fight through that phase and be determined to keep alive, keep going. Gremlin Radio Eventually however, the conditions will overcome him and his temperature will fall below a level of consciousness and he'd die. Arghh! If my body temperature drops by six degrees, I'll lose consciousness and death is inevitable. He's in pain now. Oh, God...! I don't want to be here. It's time to pull him out, he's had enough. You've had enough. How are you? You're bitterly cold. Were you shivering a lot? Are your muscles stiff? My toes feel they'll fall off. Your muscles are stiff, you can hardly talk. Let's get you warmed up and check you out. In the real world, we need our brains to survive. If I can't last minutes in minus , how will I survive here at minus ? Erik Bruin and Mads Vadel must know. They've the most extreme tour of duty in the world. Three months at a time, the Danish Sirius Patrol travel the wastelands of north-eastern Greenland with only their training and a dog sled for protection. For the next hours, I'll join them to find out how they survive in nature's freezer. Hi, Erik. Hi, I'm Donal. My partner, Mads. Welcome to Greenland. These are your dogs? They're wonderful, beautiful, gorgeous. They don't bite? No. It's time to go. (Gremlin Radio) (REPEATS THE NAME) It didn't work! That's how you start, how you learn. Learn to ski before becoming a member of the Sirius Patrol! It was the weather that first brought them here. In WWII, the Danish had to defend Greenland from the Germans, because knowing the weather here, you can predict it in Europe. Today, the biggest threat to their patch is from the seals - and of course amateurs like me. Still, highly-trained professionals like Erik, Mads and... me, are vigilant. Gremlin Radio and snowstorms can strike without warning, and cold is a constant threat. Temperatures regularly fall below minus . Whoah! Being out in the cold, absolutely everything freezes, including my left eyelid. I've been told that if your eyelid freezes like that, put your hand to it to melt it, then you can open your eye. It's dangerous to try to pull it open. I'll give it a try. I can feel it melting, that's a good thing. I feel as cold as I probably look... now that's fine. It shows that you've to be careful, cold is a killer. As night falls, the temperature plummets. There's only one tent, so what happens to me? I'm about to be buried alive. Digging a hole deep into the snow can offer life-saving shelter, or so I'm told. What do we do? We start making an entrance, then dig in, making it as long as you are, in that direction. You will lie about here. Now we dig in and start. OK. That's my home, excellent. Your home. Shall I go in? I'll spend a night alone as the temperature drops below minus . I'm a bit apprehensive about being buried alive out here. All I'll have is a sleeping bag and some candles. It's about a metre and a half high, two and a half metres long, and... about... a metre and a half wide.