The Millets sales assistant could tell I had never been trekking before. All those hopelessly naive questions about thermal underwear, mosquito repellents, mountain walking sticks, waterproof wear, boots and rucksacks gave the game away. At home, I stuck everything into the rucksack (including the instructions on how to pack it properly), strapped and belted on the unwieldy shapeless result before walking towards Leeds station looking like John Bunyan's pilgrim. Halfway up some steps, I realised I had mistakenly packed, rather than pocketed, my senior rail card. I unstrapped my right arm, the rucksack swung rapidly to my left; I lost my balance, and fell back down the steps. How was I going to negotiate the Himalayas?

I thought back to the eagerness with which I had drunkenly agreed to spend a few days trekking on the Afghan border after an encounter with Jonny Bealby, owner of adventure company Wild Frontiers, at the Groucho Club. There was no turning back now.

Members of the Wild Frontiers team met my dawn flight at Islamabad airport. Jetlagged and saturated with perpetual intramuscular fixes from nicotine patches, I prepared myself for the 16-hour drive to the Afghan border. The first stop was Peshawar. I hadn't been there for more than 20 years but remembered where Salim, an old friend of mine, kept a gun shop, one of his many businesses. An older and more dignified Salim sat outside the shop, which hadn't changed in any way. We hugged. It took him less than a minute to embark on his favourite pastime, giving informed monologues about politics and spies. The Wild Frontiers team listened with undisguised interest.

'DH Marks, I heard you were in my country. There have been great changes since your last visit.' He stuck a small piece of hashish into my pocket. 'So, would you like to buy a gun?'

'No thanks, Salim. I'm not returning to Heathrow with one of those.'

'I can arrange delivery.' Salim was laughing, but I am still not sure if he was joking.

Next stop was Dir, a city not known for its excitement. At the Dir Hotel, Jonny was standing with a tour group comprising two men and 11 women.

'You never told me you were running a white slave racket, Jonny.'

'It's normal, Howard, we always get far more women than men.'

I filed that in a few memory cells.

'See the jeeps? Here comes Muftah. He's in charge of all five.'

Muftah, a magnificent looking northern tribesman, sidled up to the car, shook my hand and gave me those 'I know you smoke dope' eyes. I smiled, equally knowingly.

We set off in Muftah's jeeps, which soon stopped at a police checkpoint. I felt an odd mixture of nostalgia, déjà vu and nausea as the cops inspected us. Muftah started shouting. Suddenly, the cops commanded us to follow them. Another police truck joined the rear.

'Are we getting busted?'

'No, the exact opposite,' laughed Jonny. 'The Pakistani police are escorting us for our safety.'

'Do they escort all tourists coming here?'

'They use their discretion. With this many women, they would obviously say yes - for a variety of reasons.'

The convoy of Muftah's jeeps and police trucks scrambled up the weather-ravaged road to the Lowari pass, where the grass began to turn into ice. A one-roomed kitchen-cum-restaurant with a prayer mat and smoking area welcomed us at the summit and served us bhindi curry and tea, which hit the spot.

Then Muftah's jeeps swooped down through about 50 horseshoe and hairpin bends; bizarrely and beautifully painted trucks, moving like snails, crawled up in the opposite direction. The slopes were littered with the wrecks of ramshackle, overloaded and incompetently driven buses and trucks that had fallen off the road into ravines. I started to feel scared - or was it delayed altitude sickness, or was I just knackered? Or stoned? A few of the police escort in front were sitting on a bench in the back of their truck, their rifles pointing, albeit nonchalantly rather than deliberately, straight at us. I felt worse.

Hot shafts of blinding white light streaked into my eyes and woke me up. I could hear running water. I couldn't remember going to bed, but had woken up in a well-appointed wooden summerhouse. I opened the door and walked into a tastefully landscaped ornamental garden. In the distance, but so big it seemed to be right there, was the white mass of Tirich Mir (King of Darkness), so named because of the size of its shadows. At 7,700 metres, it is the governor of the Hindu Kush. I was looking at the largest density of mountains in the world, which hid valleys so isolated that until recently each was a separate kingdom. Memory kicked in. I had arrived here last night after a 16-hour drive.

I joined the group for breakfast and learnt that we were staying at the residence of Maqsood ul-Mulk, Prince of Ayun, a charming, intelligent host whose family have ruled Chitral for ages. He was taking us to the local school later in the morning.

After lunch, there were three options - a short trek in the Hindu Kush, a long trek in the Hindu Kush, or going to Chitral to watch a polo match. I did not find the choice difficult.

Muftah parked our jeep at Chitral's Mountain Inn, which had been open since 1968 when its guests were mainly hashish-hungry hippies on the Paradise Trail from Europe to Asia. I got out and walked through the town centre. Guide books warn of unseen eyes observing and weighted whispers winding their way to the police, Pakistani secret service, MI6, the CIA and the Taliban.

Symptoms of ferocious hostility, however, seemed to be confined to the Chitral polo ground, where tension, excitement and euphoria often far exceed the heights reached at Wembley. I took my place in the stand, leant on a handy metal pole and began taking photographs of the furious match. Within a minute, the metal pole emitted a deafening ring: one of the polo players had completely mishit the puck, which had struck the pole two inches from my face. The trek options would have been safer.

To help me recover from the shock, Muftah drove me to the Hindu Kush Heights hotel for a refreshing drink and stretch of the eyes. It's owned by Maqsood ul-Mulk's cousin, Prince Siraj ul-Mulk. Robert De Niro and Pakistan's President, General Pervez Musharraf, have stayed there. So did Winston (grandson of the PM) and Luce Churchill, who wrote in the visitors' book 10 years ago: '...so glad that the Churchills and ul-Mulks are no longer at war'.

The Afghan border was a few miles to the west, just the other side of my final destination, the valleys of the Kafir Kalash (the name translates as 'infidel wearers of black'), once part of an area known as Kafiristan, the setting for Kipling's The Man Who Would Be King. A century ago, all the Afghan Kafirs were forcibly converted to Islam (the alternative was execution) and their homeland became Nuristan (Country of the Enlightened), a province of Afghanistan.

Gentler attempts were made to convert Kafirs living in today's Pakistan, but their resistance has ensured the continuation of their own pagan religion, culture and habits. Despite its association with Islamic fundamentalists, Pakistan allows freedom of religion. There are churches, at least one synagogue, Hindu temples and pagan sacrificial altars. Next morning, Muftah's jeeps snaked from Ayun to Kafiristan, ending up on a rough surface chiselled into the mountainside, barely wide enough for a car, impassable for part of the winter, and intermittently blocked for the rest by avalanches of stones and rubble caused by melting snow.

We entered the Rumbur Valley, one of three inhabited 'Black Infidel' valleys. Giant walnut trees bowed down over fast-flowing streams, grapevines trapped mulberry and apricot trees in their webs, evergreen oaks and Himalayan cedars enveloped the 2,000-metre summits, and lush fields of vegetable and cereal crops carpeted the rugged valley floor.

The Kalash men wear regular and unassuming shalwar-kameez, the same as their Muslim neighbours. They manage the livestock, mainly goats, taking them up the mountains for several months to produce milk and cheese. The women wear nun-like black woollen robes tied with black sash belts. Strings of multi-coloured beads hang from their necks, five plaits of hair lie generously under a regal headdress sown with rows of cowrie shells and bright buttons, topped with a massive red woollen ball.

They dance by stomping and shuffling their way through an intricate series of cartwheels and polka-step circles. Drums and handclaps provide the rhythm; flutes, shrill penny whistles and catcalls the accompaniment. The women till the land, pick the fruit and prepare the food. Both sexes are heavily into their surprisingly palatable and strong red wine. Most have fair skin and blue eyes and are shown by DNA studies, linguistic similarities and historical and oral traditions to be descended from the armies of Alexander the Great.

As we approached, several people on the roadside came running up screaming, 'Jonny Taliban. Jonny Taliban!'

'Aren't you worried by that nickname?' I asked Jonny.

'It's a bit unnerving I know, Howard, but Taliban actually means a seeker of the truth. I feel honoured.'

Saifullah Jan, the first Kalash man to be educated outside the valley (a year's law course in Peshawar) and chief representative for the people, lives in the village of Balangaru. He is a champion when it comes to protecting the Kalash timber, walnuts (their main source of protein), land and grazing rights. Our guesthouse is also run by Saifullah; previous guests include Michael Palin and virtually every anthropologist who has visited the valley.

I dumped my bags and went for a stroll through the village. A maze of channels consisting of wooden aqueducts, stone buttresses and mini-canals distributed roaring torrents of water, providing laundry areas, sanitation and hydroelectric power (from dusk to dawn only). A water-driven barley mill and row of granaries stood next to houses, which are built of wood, mud and stone in such a way that the balcony of one is the roof of another. I carried on to the sacred sanctuary. Surrounded by trees and geometrically designed wooden statues, dried branches lay ready for ignition on the bloodstained altar.

Bashali (inhabited by women while menstruating or giving birth) feature predominantly in Kalash culture. I had assumed that bashali were male-crafted prison-like institutions. Back at Saifullah's guesthouse, Jonny put me right. Kalash women are tough as old boots, athletic, fashion-conscious and incredibly beautiful. They work in the fields wearing elaborate dresses sparkling like rainbows, each individually designed and made by the wearer to express her personality and creative powers. Bashali exist because women want them.

'Anyway,' said Jonny with a glint in his eyes, 'a Kalash lady is joining the group for dinner tonight. You can ask her.'

Halfway through a goat-and-vegetable curry, we were joined by a woman clad in Kalash clothes. She was Japanese.

Either sex may marry a spouse of any nationality or religion. Bigamy, though rare, is allowed. Akiko Wada, our dinner guest, had married a man from Rumbur and divorced him, but remains fully integrated into the community.

At the core of all Kalash cosmology are the concepts of onjesta and pragata energies. Nangar Dehar, the greatest Kalash shaman and initiator of most Kalash rituals, entered a trance and shot two arrows, one red, one black. The black arrow's landing place was to be the sacrificial altar and centre of onjesta energy, to be visited by only men; the red arrow's, the bashali and centre of pragata energy, to be visited by only women.

All life forms, places and objects are accorded measures of onjesta and pragata. Generally, wine, water, holy sites, men and goats head the onjesta list, while women, Muslims and chickens are the main carriers of pragata. There is communal concern to keep the equally important energies separate. When women attend the bashali, their men do their normal daily tasks. In the bashali women can be creative and resolve personal issues without the stress of village life.

'You have any questions for me?' Saifullah asked, pouring me a huge glass of wine.

'Are you really descended from the Greeks?'

'I hope not. It is not the only theory. I'd prefer my ancestors to be Italian.'

'But what we call Italy today used to be part of Ancient Greece.'

'I think it's better if we're Italian. I don't know why.' Further questions revealed that there were no prisons or police in the valleys. And no written laws, or written language.

'Our spiritual leaders, kazis [judges], maintain our legends. They can recite or sing all 4,000 of them. They will teach their sons to do the same. The shaman communicates with our gods to find out what needs to be done and informs us.'

'What if a Kalash does something that is obviously wrong, like killing someone or stealing goats?'

'It never happens. It couldn't.'

'But if it did?"

'We would ask the shaman what to do.'

'What might he instruct?'

'To sacrifice an animal, so the village eats well, and we can all get drunk.'

I began to understand, or thought I did: there was no good and evil, just onjesta and pragata and their tricky identification and management.

Yet more wine landed on the table. Full of mirth, we drank ourselves under it and squatted on the grass.

'It's a strange one, Jonny; peace, tranquillity and merriment on the front line.'

'I know, I was here on 11 September 2001, but didn't find out anything about the twin towers until 10 days later. These valleys protect you from everything, especially yourself. It is a pity you leave so soon. Did you know the Kalash don't have a word for goodbye? They never leave here; otherwise they lose their identity.'

'I'll be back, Jonny.'

'I know. You must go for a trek next time. Maybe over that mountain there to Afghanistan.'

Essentials

Howard Marks travelled with Wild Frontiers (020 7736 3968; www.wildfrontiers.co.uk). The next trip to Pakistan is the 18-day Hindu Kush adventure which departs on 4 September and visits the Hindu Kush, Kalash Valleys, Hunza and the Karakoram Highway.

The price is £1,600 including all accommodation, guides, meals and transport but not flights. British Airways (0844 493 0787; www.ba.com) flies to Islamabad with fares from around £550. There is also a Pakistan tour departing 2 October.