The World's Toughest Guerrilla Graffiti Artists

It's unbelievably cold. Frozen vodka cold. I know because I have an armload of it and temperatures in Ulaanbaatar, the world's coldest city, have just dropped below - 50C. I'm on a solo mission to witness one of the strangest subcultures I've ever encountered; Mongolia's homeless sewer youth. Deep under the city runs a network of old heating pipes. When the USSR fell, workers left a ghost town of heated runways below the city. I was told that if I was lucky, I could witness a rare artistic ritual.
Tonight I'm lowering myself into a new hole on the outskirts of the city. All I can afford to carry is my camera and gifts for the people I encounter; vodka and Chinese firecrackers. The first thing I see is shiny shoes. It's indicative of the novel obsession with cleanliness that Mongolians seem to have, and the room is no different.
Neat rows of candles line the heating pipe. There's a set of mismatching mugs stacked on a burnt out computer monitor in one corner. Seven young men and women, dressed in tattered layers of felt, sit around the centrepiece; an neatly flattened poster of 1970's English rock band 'Smokie'. These are the first generation in Mongolia to be raised outside of Soviet control.
After shaky introductions and several rounds of cheap vodka, we head out into the network of tunnels, there's no heating here, and I can only see our white eyelashes and hair as we walk through the dark. I don't want to seem weak in front of the world's toughest guerrilla graffiti artists though.
In the depths of winter, they collect bottles in the streets, earning a meagre enough income to buy cheap spray paints. They have developed a distinct technique that can only be achieved when the paint freezes as it leaves the can, producing thin jagged lines. They must replace cans every thirty seconds.
As I leave the sewers in the early morning I look back in disbelief at the people I spent the night with. Hardy, young, motivated. The 6ft letters 'democracy' frozen on the walls.