Bach from Murray Perahia

There's no one quite like Bach. Every time I hear the Aria from his Goldberg Variations – a keyboard masterpiece written, so the story goes, to soothe an insomniac Russian ambassador – I feel myself pause and forget whatever I've been doing. It's music of the most beautiful serenity. Here it is performed by the superlative Murray Perahia.

The Summit

We start to walk at midnight. It's cold but, for once in my life, I don't feel it. Probably because I am wearing two pairs of thermals, trousers, waterproof trousers, inner socks, outer socks, a thermal vest, a long-sleeved thermal top, a fleece, a fleece gilet, two pairs of gloves, walking boots, a down jacket, a fleece scarf and a hat. And my big rucksack and a head torch. In the bag I have put another large fleece. I'm not taking any chances. My camera battery is in an inside pocket to keep it cosy, and my water bottle and camelbak – a sort of pouch with drinking tube – are wrapped up tight to stop them freezing. We've all been instructed to blow into the camelbak's tube after drinking in order to push all the water back inside, or at your next drink you'll be greeted with ice.

It's the day before the full moon. It's almost as if it's watching over us, choosing to light our way. We almost don't need the torches as we start our long trudge to the top. The aim is to reach Gilman's Point, at the edge of the crater, for sunrise. If you imagine taking one step, counting to three, then taking another, that's about the pace we went at. We were only going gently uphill – the crater sides are offputtingly steep but we're zig-zagging – yet we're all out of breath, huffing and puffing as if we were running a marathon. I can make out another group ahead of us, slowly moving dots of light. There's a small frisson of gloating as we overtake them. But at our first break, it's clear some people are already feeling the strain. I munch a couple of the sugary biscuits I've been given as a snack, while others eat their Dairy Milk chocolate. It gives them energy but seems to make everyone feel ill; for once I'm glad that I have to have the non-dairy option. It's too cold to loiter, so we're soon on the move again.

The guides start to sing. A solo voice sings a line, the rest respond. It's unexpected, magical and completely surreal. Am I really here, climbing up this mountain in the early hours of the morning, with the moon and music?

The combination of painful effort and nausea remind me that, yes, indeed, I am really here. Someone tells us a story about one of his friends who is an ultramarathon runner. When you run a regular marathon, he says, you start to question why you're doing it, why you're pushing yourself through such gruelling pain. In an ideal world, you come through that stage on a new high, full of positive energy ad belief that you are on the right path. When you run an ultramarathon, the questioning is commensurately more profound: you start to question your existence, what you're doing with your life, are you in the right job, the right relationship, doing the right thing? I reckon you can see it as raw honesty with yourself or self-torture. Either way, it's an exposed place to be. And it's not somewhere I really want to go, psychologically speaking, while I'm on this mountain.

As we plod closer to the top, though, it gets harder and harder to convince myself to keep going. I try to stop my thoughts. Huh. Harder than you think. I resort to counting from one to a hundred, over and over. It's dull, but it does the trick. I can see lights above us: are they path-markers, trekkers or stars?

The ground underneath has been dusty most of the way up but towards the upper reaches of the path it becomes stony and rocky. Our guide points towards the top, saying it's not far now, but it's so hard to tell whether there's more rock behind what we can see that I decide not to look or trust him and just keep on trudging. The rocks become bigger and bigger, and we have to scramble and climb. For some reason, it feels less difficult than it should do. Then I realise that I'm being given a helping push by one of the guys in the group. (Thank you!) As we near the top, our guide tells us it's just ten minutes away. None of us believe him and someone decides to have a bet with him. I've gone into a sort of semi-comatose state now. One of the Aussies chooses this moment to reveal he's actually scared of heights... It actually does feel pretty high up when I look - the jagged peaks of Mawenzi which have been towering over us the past days are now below us – and I start to wonder how we'll get back down.

And then we're at Gilman's Point. 5,681 metres up. We came round some rocks to find not, as before, more of a climb, but instead the flat edge of the crater rim and a big green sign congratulating us. We pose in front of it, taking photos. I'm frozen and exhausted. I feel like I should eat for energy but I don' have the appetite. All twelve of us have made it to Gilman's. The sun has risen, nature's great metaphor. We barely have any time before one of the guides is shepherding us on to get round to Uhuru, the highest point of Kilimanjaro. Now or never. At first, I think I can't do it. Sitting here now, writing this, I'm shouting at myself. You were going to go back down? After all that effort! Just keep going!

Four or five people have gone ahead, and I rush after them - deciding to give it a go. But the pace is fast, and after a few minutes I just feel so tired. I sit down and say I'm going to go back. Another woman in the group comes back, asks if I'm sick - I'm not – and says, forcefully: 'I'm not going to be the only woman in this group to make it to the top. You're coming with us'. That was possibly the best thing she could have said. (And thank you too!) One of the brilliant guides runs back to ask what's wrong, and when I say I'm tired, he says that's no excuse, takes my backpack, asks why it's so heavy (the fleece!) and then we're on the move again.

As we make our way round the crater edge, we start to see a few people coming back down from the summit. One young woman is stumbling and being supported by a guide. Up here, there's only half the oxygen you need. It feels like being drunk and hung-over at the same time. We make several stops to look at the fantastic views and rest. The two tallest men in the group seem to be suffering the worst. One curls up by the side of the path and is sick. Another keeps on collapsing on his bag, saying, with no small hint of melodrama, 'go on without me'.

We keep on going. Past Stella Point, until the path to Uhuru Peak is finally in view, clear ahead of us. It's a race to the finish (though who made it to there first is still being disputed). We've made it to the top! It is a fantastic feeling: looking out from the top of Africa, the summit of the highest free-standing mountain in the world. We are at Uhuru, which, in Swahili, means 'freedom'. It's gloriously clear: blue skies, warm sun. Photo-perfect.

We join the queue to take photos in front of the sign. It's quite busy. Three Italians push in front of us, causing one member of our group to tell them in no uncertain terms that we've got 'ill people here' and we have to take our pictures now. The slight exaggeration works. We get our photos, alone, in groups, with the various charity flags and posters people have brought with them.

Ten minutes or so is all you get at the top, and then the long journey back down begins. I start ahead of the group, and, actually, it's just a wonderful feeling walking through this incredible, alien landscape, white snow glistening under the peachy sun. There's a magnificent glacier to one side, the intriguing bowl of the crater to the other.

It takes between an hour and an hour and a half to get back to Gilman's, where the descent begins. If going up the mountain seemed tough, then going down the mountain is tougher still. The dust is nearly a foot deep, and slippy. I start to carefully pick my way down the path, but it's clear I'm going too slowly. One of the guides grabs my arm and we start to 'ski', sliding and skidding in giant steps, throwing up clouds of dust. We chat as we go: he tells me about his wife and children, we compare the price of food in England and Africa, he tells me about how he used to be a teacher but then became a guide. One day, he says, he'd like to be a chief guide. I am sure he will.

Nearly three and a half hours after leaving the summit, I arrive back in camp. I feel elated. I did it!

Time for a rest. Into the tent: my feet hurt, and I feel like I have pins and needles in my brain. No joke. It's not a comfortable sleep. And a little over an hour later, we're up again to eat before we have to start trekking to our next camp. People are returning one by one, at their own pace. When we sit down for lunch (only lunch! It feels like we've packed a week's worth of experience into the past twelve hours) some of us are feeling the sense of achievement (We made it to the top!), others are suffering. One trekker needs oxygen after his asthma starts playing up thanks to the dust. Another refuses to talk about it, saying it's both the best thing she's done and the most miserable day of her life.

After lunch, we pack and are on the move again. There's no drinking water at Kibo, so we need to get to the next camp down for the night. And to make away for any other groups arriving to attempt the summit. It's a fourish-hour walk back across the Lunar Desert, this time peeling to the right down the Marangu route. It's actually good to stretch out tired limbs with a walk over flat ground. And when we reach the next camp down, the air is already a little richer and the mountain top already looks like a distant reality. Food, cards, gossip, sorting out of the tips for the guides and porters, and it's time for sleep. I've been to the summit of Kilimanjaro. And I can't stop smiling.

This is my fifth post about my trip-of-a-lifetime climbing Mount Kilimanjaro and going on safari in Tanzania. I'm raising money for Water Aid so if you would like to sponsor me, please click here. So far I've raised £780. Thank you so much to everyone who was given money. It is going to a great charity.

Notes on Australia

• Verdi at Uluru and Sounds of Australia: my reviews of the two concerts at Uluru for BBC Music Magazine. And here are links to articles by two of my fellow Uluru journalists: Limelight Magazine; Vogue Italia.

• Just discovered this great website today, The Iron Ammonite. It includes amazing aerial photos taken from commercial flights. The photographer is Paul Williams, who works at the BBC's Natural History unit here in Bristol. On my flight from Darwin at the Top End of Australia (the naming is that literal) to Perth, down in the South West corner, I spent most of the time looking out of the window at the incredible red desert landscape, with its dried out river beds etched into the ground in snake-like meanders. Sometimes a brilliant flash would catch my eye, and a small pocket of water would be revealed – like a precious jewel buried in the sand. You can see Wiliams's Flickr set of photographs here, and I've posted his photo of Uluru from the air above.

• And, next weekend, I'm hoping to go to see the Australia exhibition at the Royal Academy, billed as the first major exhibition in the UK on the continent's art for 50 years.