The day started well enough: warm (in fact my brother tells me it's colder where he lives in the Swiss Alps right now, though we'll be back in the minus thirties on the Plateau), a bit of cloud but still enough sunlight to give us the surface contrast we need to navigate easily, and the slightest of headwinds.

We dismantled the tent and set off up the glacier, beneath the sight of a hazy parhelion above the Cloudmaker and a weird-looking bank of cloud hovering below the tops of the mountains to our east. The surface was incredibly good with almost no crevasses, and through my sunglasses the snow looked a bluey-grey cream, with the sky tinted peach-coloured at the far horizon. Perhaps -I wondered to myself- I've made the mistake of using books meant for general public entertainment as reference guides; perhaps this glacier's not all that challenging after all once you've sifted through the hyperbole and drama and derring-do. My sled felt almost weightless behind me, and I wondered if we'd break some sort of Beardmore distance record today.

The rude awakening came around the third hour of the day, when the surface and terrain began to get rougher and more ridged, much like sea ice does under pressure. Our pace slowed, but I was enjoying piecing together the puzzle of finding a route and scouting out a way ahead when it was my turn to lead. By our fifth hour of the day, now going decidedly uphill, we encountered more and more patches of blue ice, upon which our skis had next-to-no grip. Short sections were fine, aside from some occasional Bambi-style flailing, but when there was more ice than snow, we switched to crampons. For the first time, I had to be sure where I placed each footstep, and the increase in nervous energy was remarkable. By all accounts the blue ice flattens out later on, but here it's incredibly fractured and riven with snow-filled cracks that are often pretty rotten and crumbly at the edges.

The big slots and holes are nearly always obvious and avoidable (and mostly bridged so well that you could drive a bus over them) so our biggest fear is not some gaping chasm, but rather putting a foot in a crack and twisting an ankle or wrenching a knee. We crossed many crevasses today, and it's been a good learning curve for me. I'm feeling infinitely less anxious about my ability to negotiate this terrain than I did a few days ago, but I'm also under no illusions about the challenges our ascent to the Plateau will hold. After nine hard hours yesterday and almost the same today, Tarka and I are both pretty spaced-out in the tent this evening. I'll sign off before I start rambling...