You couldn't have asked for a better day for a competition. It's minus five degrees, the sun's shining and there's not a breath of wind. The snow's perfect and the biathlete's in top form. He's one of the best – he can win the race. Often there's only a few thousandths of a second between the victor and the vanquished, so the gliding ability of his skis is very important. And this depends on several factors, not least whether the wax mixture he's applied suits the particular type of snow.