It's a feat of mental and physical willpower to conquer mighty Kilimanjaro and Vanessa James is determined to master the mighty mountain.
At the last pit stop before the summit of Kilimanjaro, I hit the wall. Screaming from altitude sickness, frozen in the bitter wind, it's like I'm watching myself from somewhere else.
I hear the rising panic in the voice of my climbing companion Geoff as he pleads with one of our guides, Harold: "Would it not be better if she rested?"
But it's below freezing.
"Better to rest at the hut," Harold replies.
He takes my backpack and leads me up the barren slope a few steps at a time, towards Kibo Hut, perched tauntingly on the rocks 1.5km away.
As I struggle on through the bleak landscape, it's hard to believe that just two days ago our group of seven started an attempt on the world's highest freestanding mountain in hot sunshine with an easy walk through lush rainforest draped with curtains of hanging moss, begonias, violets, and orchids.
As we got higher the verdant rainforest started to dry, the cloud descended and the air chilled. By our first overnight stop, Mandara Huts at 2800 metres, the cloud had closed in. On a clear day you can see all the way down to the town of Moshi from the Maundi crater rim. We could barely see across the crater.
The next day we set out in fog for Horombo Hut, another 1000m ascent through easy terrain. It was freezing and we were fully kitted out in jackets, gloves and woollen hats, except for Spencer who wore his Rip Curl board shorts (he's Australian).
"Pole, pole," our lead guide, Fatael, kept reminding us. Slowly, slowly is the way to climb Mt Kilimanjaro. At 65 years old, Fatael strolls up Kilimanjaro every Monday in his corduroy trousers and sneakers.
Wildflower territory gave way to huge twists of sticks swirling in the low cloud, then giant groundsel spiking out of rocks as if Dr Seuss was illustrating the landscape for us.
And then today. This morning the track led us quickly out of the moorland, heather merging into tussock and straw daisies. The cloud swelled and billowed down the mountain in bulges of grey and white nimbostratus.
Soon icy rain started to fall and the biting wind drove grit and hail into our faces. Somewhere across the saddle we huddled under a low wall of rocks for lunch, pelted by rain and stones. I couldn't eat anything. It was very, very cold. By the time we reached the last pit stop, I could hardly walk.
And now I'm gripping Harold's fat ski glove and scraping my feet up this desolate slope. Finally, he leads me into Kibo Hut. It's a big stone hut and the bunks are all in one room. Taking off my balaclava and boots, I crawl under my sleeping bag. Another climber, Leanne, asks if I'm alright but I can't talk. All I can manage is a thumbs up.
About an hour later I wake up feeling as if my very bones are frozen. I'm shuddering with cold from the inside out. I put on leggings, trackpants, waterproof overtrousers, a woollen hat and a borrowed down jacket. My bunk is on an outside wall and leaning on the stone, even with five layers on, is like lying on a block of ice.
Dinner is at 5pm, then we sleep until 11pm, ready to start our final ascent by lamplight. We are now at the base of Kibo Peak and the next thousand metres is incredibly steep. This is where the real challenge begins.
When our guides arrive to take us to the summit, the youngest member of our group, Angela, is too sick to get up. I've warmed up and feel okay to go but as we start out Harold says, "You're wearing too much." By the time I've taken off my icebreaker and put my fleece and jacket back on, the others are gone in a dark lit only by their headlamps. Harold and I set off together.
Before long an extreme exhaustion comes over me and as I close my eyes I'm dreaming. I lean forward on my sticks. Great swirls of lives and people rush in. I can see beaches and the ocean, and I'm surfing, no, flying. "Come on," Harold says, "Walk now."
His voice is far away. I open my eyes to the mountain, the darkness, the thin air. Other groups shuffle past. Looking up, lights from the other climbers are impossibly high, zigzagging endlessly on and on up the mountain.
"Don't look up," Harold says, "Three more corners, then the 5000m sign."
"Five thousand metres!" I splutter in disbelief. "We've only come 250 metres from Kibo Hut?"
"It's good," Harold says calmly.
When we stop at the sign I check my watch. It's 3.41am. We've been climbing for three and a half hours.
"Maybe two more hours," Harold says.
I think I can do that. Through the clear sky the tiny lights of the villages are sprinkled across the plains far below, twinkling like clusters of stars. Harold is singing "We are climbing Kilimanjaro ..."
He points up. "Three more corners," he says, "and the scree. That's easier, because it's zigzagging." I know by now that what Harold thinks of as corners are not the same as what I think of as corners. Finally we get to the scree, but zigzagging doesn't make struggling through the loose rocks any easier.
Light leaks from behind the cloud and breaks in a brilliant streak of glowing orange and gold behind Mawenzi, the lower peak. As the sun spills across the mountainside like molten amber it reveals a satellite picture of the saddle, all the way back down to Kibo Hut, a tiny speck in the rocks, and across the countryside to the plains and lakes of Tanzania.
The final part of the ascent is through huge rocks iced with a crisp frost. Harold points out a guide coming down with someone from our group. Geoff is right beside me before he recognises me.
"Vanessa!" he exclaims excitedly. "You've made it!" He's fallen several times, once landing heavily on his stick and splitting it completely in two. He's drunk with altitude sickness and doesn't even bruise.
At 6.30am Harold and I reach Gilman's Point on the crater rim. We're above the clouds and the world goes on for ever. The maw of the crater gapes across the top of the peak, swept through with a smooth grey dust. Massive blocks of ice are stacked on the other side of the crater. Nothing moves. We're part of a world frozen in time.
I sit down to put on sunscreen. My icebreaker, under the bungee cords on my pack, is frozen solid.
From Gilman's it's one and a half hours around the crater rim to Uhuru Peak, the highest point. The guides have the final say on whether their climbers can attempt this last stretch.
Harold asks if I want to go on. As much as I want to, my legs are shaking and I haven't eaten in nearly 24 hours. I say no.
About halfway back to Kibo Hut, great rolls of cloud unfurl themselves over the mountainside, blanketing out Mawenzi, the saddle, the plains. Climbing at night is the only way to guarantee the views.
Spencer and Vicky are next back. They made it to Uhuru but "I was just crying," Vicky says and Spencer is sick. Honeymooners Leanne and Justin fared better and took stunning photographs of the glaciers and ice formations.
We rest for a few hours before starting out for Horombo about mid-morning. The cloud lifts and the trail winds ahead of us for miles across the alpine desert. My head clears and the sickness dissipates, replaced by euphoria at what I've just achieved.
Day five is clear and crisp for our final descent. In the rainforest we see grey baboons feeding. A family of colobus monkeys run across the trail, their long silky white hair flowing out behind them.
In fading evening light we gather outside the Marangu hotel bar to thank our 16 guides, porters, and cook.
Spencer crunches the numbers and tells us our group fits the stats exactly: one person got as far as Kibo, two to Gilman's, and four to Uhuru.
Angela and Geoff agree that it's the hardest thing they've ever done in their lives - not just physically but psychologically.
Me? I have unfinished business with that mountain. I'll be back.
Getting there: Air New Zealand has daily services to Nairobi, Kenya, in conjunction with partner airlines via Perth and Johannesburg, with economy class return fares from $3296 per person. Precision Air and Kenya Airways operate between Nairobi and Kilimanjaro, Tanzania.
Getting around: Most organised treks offer a shuttle service (at extra cost) from Kilimanjaro Airport to your hotel. It's also possible to travel overland by shuttle from Nairobi to Kilimanjaro but this takes about eight hours.
Vanessa James paid her own way to the top of Kilimanjaro.