He was the old Etonian heir to a £100m fortune. He was close to the Kennedys and almost married a Heseltine. He'd been a Wall Street broker and a war correspondent. He'd even been a leader of the Mujahideen. So why did Carlos Mavroleon die of a heroin overdose in a rundown hotel near the Afghan border?

Peshawar is a rough town. Its bazaars are thick with suppressed violence and its traders rarely smile. Five times a day the call to prayer howls through the air in a clatter of static and guttural vowels. At night the roads rattle with automatic gunfire and it is impossible to tell if there has been a wedding or an assassination.

Many people die in Peshawar, violently or otherwise. Nobody chooses to end their days there. No one asks for his ashes to be scattered in the churned mud of the Storytellers Bazaar or from the battlements of the Purana Qila, the old fort. To the west of the city, the Khyber Pass leads up through the dusty, rocky hills of the Hindu Kush towards the border with Afghanistan. When the pollution above the city clears, the hills are sharp against a very blue sky. But they are gritty, sullen mountains and no traveller wants his bones to lie among them.

Carlos Mavroleon didn't want to die here. Certainly not in the small, claustrophobic hotel room where they found his heroin-soaked body, on 27 August 1998. Carlos didn't want to die anywhere. Perhaps more than at any other time in his incredible life, Carlos wanted to be alive.

He had packed it in to his 40 years. The old Etonian heir to a £100m fortune, he had been a war correspondent, a Wall Street broker, a lover of glamorous women from glamorous political dynasties (the Kennedys) and from less glamorous ones (the Heseltines). He had been a cool, gimlet-eyed war reporter, blowing off the tension of his assignments in the bars and clubs of Notting Hill. He had commanded a unit of Afghan Mujahideen against the Red Army and had been a bodyguard for a Pakistani tribal chief. And, for most of his adult life, Carlos had been a regular user of speed, coke, Ecstasy, heroin and enough pharmaceutical products to stock a large, if specialised, chemist.

But through it all, it seems, he knew what he was doing. Carlos was rarely, if ever, out of control. He pushed it to the edge, looked over - and came back again. And again and again and again. Except in Peshawar on that stinking hot August day two years ago.

On 7 August 1998, two massive blasts devastated the American embassies in Tanzania and Kenya and killed more than 200 people. American investigators followed the trail of the bombers from East Africa to Pakistan and on, via Peshawar, into eastern Afghanistan. Thirteen days after the explosions, President Clinton launched 75 cruise missiles against the camps that the CIA believed were run by Osama Bin Laden, the terrorist mastermind supposedly behind the attacks. It was called, slightly optimistically, Operation Infinite Reach, and successfully killed a dozen or so young Pakistanis who were training in the camps as well several blameless old men and a large number of goats. When the missiles went in, I was in Kandahar, a fiercely Islamic city in the desert south of Afghanistan. We heard of the attack at about midnight and I spent much of the night filing to my newspaper. It was only at dawn that I really began to realise the situation. We sat tight in the United Nations compound and listened to the radio and the chanting from the mosque.

Feelings ran high in the aftermath of the strike. In Kandahar, it took a long speech from the most senior cleric in the city to stop the mob marching on us. In Kabul, the capital 300 miles to the north, two UN peacekeepers were machine-gunned, one fatally. There were huge demonstrations against the Americans across Pakistan. Reports started circulating in Peshawar that a bounty of $15,000 had been offered by Bin Laden for dead Westerners.

Carlos was staying with his family at his father's seaside home in Athens when the missiles went in. He arrived back at his flat in Fulham, west London, to find 12 messages winking at him on the answerphone. Carlos was known to other journalists as a 'shithole specialist'. The worse the war, the deeper the poverty, the nastier the place, the better Carlos liked it. His favourite shithole was Afghanistan. The calls on his answerphone can't have been unexpected. He rang CBS, the American TV network, to accept an assignment for their flagship Sixty Minutes programme. Leslie Cockburn, the producer at CBS, knew him well. 'I can't imagine why you are calling,' he joked when he called her. 'By the way, I have a multiple Afghan visa.'

CBS wanted him to get to Peshawar as soon as possible to try to get to the camps. The hardline Taliban militia who ruled much of Afghanistan - including the bit I was stuck in - were not letting any journalists into Afghanistan. To get into the country would mean travelling in disguise. It would be very risky. Even a team of Afghan journalists had been badly beaten up and narrowly escaped execution when they tried the same exercise. But if anyone could pull it off, he could. Carlos called his fiancée, a 26-year-old TV researcher who he was due to marry in November, and then rang his father. 'Don't worry, papa, I'll be careful,' he told him. He packed his gear, picked up a $5,000 expenses advance and flew straight out to Pakistan on Emirates first class. He arrived in Peshawar on 23 August and checked into Green's hotel just off the central Saddar Bazaar. He had four days to live.

Saddar police station is only a mile from Green's hotel. Ten days after Carlos' death a smiling detective called Nisar Ali Marwat flicked a brown file on to his glass-topped desk and told me to read it. Under a slowly rotating fan, I leafed through the badly typed pages. A heavily moustached sergeant brought sweet, milky tea in stained cups. Another, sitting on a broken chair behind me, played with his handgun while I read, emptying and refilling the magazine with small, snub-nosed bullets.

The death certificate was numbered 83/98. It gave the cause of death as 'Heroin poisoning (self)'. The autopsy was conducted at 8am on 28 August by Professor Inayatur Rehman Khalil of the Khyber Medical College, Peshawar. Time of death: between 18 and 24 hours before the time of the autopsy. Carlos's body was fully rigormortised and showed no visible signs of violence. All organs were normal. The face and upper part of the chest were 'livid'. There was a blood-stained discharge from the right nostril. The left arm showed a prick-mark in the ante-cubital region and an insulin syringe contaminated with blood lay beside the body. The syringe tested positive for diacetyl morphine (heroin). Carlos's stomach also tested weakly for diacetyl morphine. There were three small packets of drugs in the room. One, opened, was diacetyl morphine. The second was crude powdered opium. The third was an antihistamine tranquilizer called chlorophenaramine maleate.

According to the police statements, Carlos was sitting upright on his bed when he was found, a cigarette between his lips. The bloody syringe was on the coffee table in front of him. There was also a blackened coin. He had died of 'heroin asphyxiation'.

A press photograph taken of his body as it was removed from the hotel shows a swarthy, good-looking man with tight, black curly hair that made him look much younger than his 40 years and a lean, muscular body. He was stripped to the waist when he died and was wearing baggy, local-style trousers.

Another sheet of paper listed his belongings: satellite phone and spare battery, camera charger, British passport B451472, small video camera, Leatherman-style knife/tool, Sony audio recorder, first-aid kit, Maglite torch, tripod and head, Sony shortwave radio stethoscope, four syringes, duty-free pack of Marlboro Lights, sewing kit, video camera battery packs and charger, two shalwar kameez (local baggy trouser and shirt), white local prayer cap, local leather sandals, Holy Koran (translation), books of Islamic history - four, $1,800 in $100 bills, $2,400 in $50 bills, and 12,265 Pakistani rupees [£150].

I read the list and looked up at Nisar Ali Marwat. The man behind me had put his pistol away. The tea cups had left oily stains on the glass of his desk. He shrugged.

When 'Bluey' Mavroleon said goodbye to his son for the last time he cannot have been too reassured by his promise to be careful. Carlos may have been kind, brave, intelligent and charming. But, by ordinary standards, he was not careful.

But then Carlos had never lived by ordinary standards. He was born in April 1958 and grew up in the rarefied air of real high society, not the ersatz Hello! version. His father is a Greek shipping tycoon who was once married to Somerset Maugham's granddaughter Camilla. She eventually left him, when Carlos was three, for Count Freddy Chandon, head of the champagne house Moët et Chandon. Carlos's mother, Giaconda, is Mexican. His brother, Nicky, is married to the filmstar Barbara Carrera. The family fortune is estimated at £100m. Carlos's address book contained phone numbers for Fawn Hall, the secretary at the heart of the Iran-Contra affair and an old flame, Barbara Streisand and Christina Onassis. He went out with Annabel Heseltine, the journalist daughter of the former deputy prime minister for two years. She wanted to marry him. When it became clear that something awful had happened to Carlos, Ethel Kennedy, wife of Bobby senior, rang the White House to find out exactly what was wrong.

In 1979, Bluey inherited the family fortune. Carlos grew up in London's Eaton and Cadogan squares and was sent to Eton but, though he did well, hated it. He started to rebel, at first in the ordinary ways; with left-wing politics, music that his parents wouldn't like, soft drugs and drink. But as ever he soon left the ordinary far behind. At 14, he left his privileged world and signed himself into a London comprehensive.

After two years of taking a lot of LSD and indulging in 'industrial scale shoplifting', he told his parents he was going to the southwest of France to stay with friends. There were no phones, he said, so they wouldn't hear from him for at least two weeks. He had calculated that would give him enough time to get free. He planned to head to Burma and smuggle rubies.

He got as far as Pakistan. High in the Hindu Kush foothills, close to the border with Afghanistan, in lands that are barely controlled by the current Pakistani administration let alone by the British Raj, Carlos did odd jobs - including bodyguard and labourer, learned to speak the guttural language of the Pashto tribesmen who looked after him and converted to Islam. He never contacted his family. They gave him up for dead.

After nearly two years, he returned to Britain and Belgravia, thin, sick and still restless. His family welcomed him back, hopeful that his youthful wanderlust was sated. Carlos worked hard to get his A levels, but played hard, too. He moved from amphetamines and acid to heroin. Before long, he had picked up a serious habit which he never entirely shook.

He may have been reckless, but he wasn't stupid. He crammed at Millfield, a top public school, and got a place at Princeton University. Not satisfied with that, he applied to Harvard and, on the strength of a successful interview and a fistful of forged references, got in to read politics. With his money and connections, he was soon mixing with the best of America's East Coast society. He was a favoured guest of the Kennedy clan. He had an affair with Mary Richardson, who later married Bobby Jnr, and a short fling with Fawn Hall.

From Harvard he went on to Wall Street. It was the 80s and Carlos, intelligent, well-connected and bold, did well. He lived in Manhattan. He made a lot of money. And spent much of it on cocaine and heroin.

And yet it wasn't enough. By 1985, the attractions of his Manhattan lifestyle had palled. He flew to Islamabad - the capital of Pakistan - and drove up to Peshawar. It was then the main headquarters and logistics base for the guerrilla groups. He introduced himself to them and convinced them to take him into Afghanistan. It was his first taste of war. Within months of returning to America he had sold the New York apartment and was on his way back to the sub-continent. He was 26.

A canal runs through Peshawar. It is full of refuse and dead animals, but the children play in it anyway. By the banks of the canal, in a bungalow set back behind high walls and a courtyard, is the Afghan Media Resource Centre (AMRC). Throughout the Afghan war, it funded journalists' trips into Afghanistan and disseminated the material they collected. It is widely believed to have been set up and supported by the CIA. Carlos used to sleep on its floor between trips 'inside'.

One of the films they have at the AMRC was taken in June 1988 near the eastern Afghan city of Jalalabad. I watched it an hour or so after reading through the police report on Carlos's death. A keen young Afghan projected it on to the only wall not covered in pictures of blown up tanks, dead guerrillas or Russian soldiers, burned out villages and downed helicopters.

First the camera pans across a field full of Mujahideen fighters. They are waiting to go into action, squatting with their weapons in lines in the sun or standing in the shade of trees. In the background are the mountains typical of eastern Afghanistan. The film flickers, jumps and weaves. A bearded, grinning Carlos appears.

'My name is Karimullah,' he says, his voice deep and unaccented. He is wearing the pakol - the beret-like woollen cap of northern Pakistan and Afghanistan - and has four curved magazines and an AK47 slung across his shoulders. He is a head taller than everyone else. His new name means 'blessed by God'.

'I am a Mujahideen,' he continues. 'We are making an attack today on the city of Jalalabad. All the Mujahideen commanders have come together for this attack. I am very happy and proud to be with my Mujahideen brothers. Allahu Akbar. God is great.' Karimullah then continues in fluent Pashto. 'I am from London. In London I fought the Jihad with a pen. Now I fight it with a sword. I have come to Afghanistan to take part in the Jihad.'

The cameraman asks if when the Jihad is over Carlos/Karimullah will bring his family to Afghanistan. 'Inshallah [God willing],' he replies with a broad smile. Carlos had arrived in Peshawar three years previously. At first he had been involved in the political side of the Mujahideen's struggle, handling foreign journalists and visiting American VIPs, but the urge to be physically involved in the action became too strong. By 1988, he was an experienced fighter and, according to former comrades-in-arms, a good one.

'When you go into battle, you do what you are told. Karimullah would do whatever he was asked and do it well,' said one former comrade. Several former fighters said that by the end of his time in Afghanistan, Carlos was in charge of a dozen men and was running ambushes by himself. He was always in the thick of any action and even prayed longer and harder than his comrades. One former Mujahideen remembered how Carlos had gone outside for dawn prayers in a freezing gale and had returned wet through. 'We laughed at him when he came back in, but he just said "Ahumdilallah [God be praised]", and lay down again.'

In 1989, the Soviets pulled out. The war carried on as the guerrillas took on the Moscow-backed government's forces, but Carlos was becoming disillusioned with the infighting among the various groups. It was time to reinvent himself again. He returned to London and within months had metamorphosed into a war correspondent. At the end of his time in Afghanistan he had worked as a cameraman and had shot footage of frontline action. With that, and his languages and charm, the work was soon rolling in. In 1991, he was in Oman trying to sneak, in disguise, into Kuwait during the Gulf War. He failed, but succeeded in getting into northern Iraq a few months later. The next assignment was Somalia, then the Sudan, Burma, Angola, Rwanda and back to Afghanistan. On several occasions, he found himself back in Peshawar. Twice he tried and failed to use his connections with the Mujahideen to get access to Osama Bin Laden.

In the early 90s, he made a number of trips to Somalia for the American networks. Tim Deagle, a journalist who had worked with Carlos in East Africa, said their time together had revealed Carlos as 'a seriously good human being'. 'Despite everything we saw - and we saw hundreds of dead bodies in a day - he never lost his compassion. We went into one village and there were about three people left uninjured and he went around giving out first aid and looking after people. Most would have just taken their pictures and left.'

Yet there was a spirit of recklessness in Carlos, a flamboyance, that seemed never to die. Deagle remembered his colleague insisted on a lunch-stop during a particularly chaotic moment during the fighting. 'He had found two lobsters, so we stopped in a field hospital with an army withdrawing around us and cooked them up and ate them with bayonets.'

On another occasion, Deagle found Carlos standing on top of a jeep with a pistol in his hand, a huge stack of dollars in the other and a crowd of angry Somali gunmen around him. 'NBC and ABC had asked him to pay off the people they had hired for protection. Carlos told them all they had to pray before he would pay them. You or I would have been executed on the spot, but he got away with it. He always did.'

In between trips, he had a number of relationships - 'women just flocked to him' according to his brother - and took a lot of cocaine. He spent time in the clubs and bars of Chelsea and Notting Hill. He read dozens of books, usually classics, and read and re-read TE Lawrence's Seven Pillars of Wisdom . He wrote book reviews for the Literary Review . Almost always he managed to keep his addiction hidden. Colleagues who he worked with closely for years never saw him take drugs. There are hints though that he did. Several people in Peshawar told me that he had got into an argument with an Afghan journalist after smoking heroin in Jalalabad. It was in 1996 after a second failed attempt to find Bin Laden. It seems Carlos didn't cope with disappointment well.

Green's hotel is gloomy and claustrophobic. Poor backpackers and wealthy Pakistanis stay there, not journalists working for American networks. Carlos's room cost £8 a night and was on the third floor facing east. From its small window there was a view of tangled electricity wires and roofs.

Carlos arrived in Peshawar on the evening of Sunday 23 August. He dumped his bags and walked a hundred or so yards to the office of The News - a local paper - to catch up with Rahimullah Yusufzai, a Pathan reporter who knows everyone and everything. If Osama Bin Laden wants to talk to the Western world he gives a statement to Rahimullah. So do the Taliban.

Rahimullah knew Carlos from the time of the Afghan war and was generous with his advice. He was happy to talk over the various ways to get to the bombed camps, even though he was trying to work out how to reach them himself. Yusufzai told Carlos what he must have suspected: that his only chance was to disguise himself as a local and work his way through the mountains and across the border. The best place to try, Rahimullah said, was from the small town of Miram Shah which is only a score or so miles from the camps themselves. The next day Carlos hired a car - a big Toyota pick-up - and a driver and set off. By nightfall he was at Bannu, a dusty town on the edge of the mountains, by late afternoon on the next day he was in Miram Shah itself.

Within hours he was picked up by Pakistani intelligence services. It was the evening of Tuesday the 25th. Though the Pakistani spooks didn't touch him, they scared him. The whole of the country was jittery after the strikes and the intelligence services were more jumpy than anyone. Despite his credentials, he must have had a hard job convincing his interrogators of his true identity and purpose. After a tense and sleepless night he was put on a bus back to Peshawar. As he was not found to be in the possession of heroin when picked up on Tuesday evening, it is fair to assume that he bought the drug after his release from custody.

Around 7.30pm the next day, Cockburn, his producer, began calling Carlos's satellite phone. It rang out every time. By the evening, she was very anxious. She called Green's and was told that Carlos had his key and was in his room which was locked. She kept trying the sat'phone. Eventually the hotel staff used a master key to open the door of the room. Carlos was dead on the bed. He had died a few hours earlier.

I arrived in Peshawar on the day Carlos died. After three days stuck in the UN compound while the authorities tried to restrain angry mobs in the streets we were finally evacuated by the UN back to Pakistan and I had driven up to Peshawar to cover the story of the missile strikes' fall-out from there. After only a few hours in the city, a local newspaper editor, Faisal Quazi, called me on my mobile to ask if I knew anything about the dead British cameraman.

That evening, Peter Jouvenal, a veteran cameraman who knew Carlos from the days of the Afghan war, mentioned over a drink that the dead man had been to Eton. Suddenly everyone wanted an answer to the same question: how did a man with so much end up dying in such a mean and sordid way? Two year's on there is still no good answer. And, as a result, though the authorities have officially closed the file, there are many who believe that the bald facts of the police report and the post-mortem are concealing something more sinister.

One thing everyone seems to agree on is that Carlos would have been unlikely to have accidentally overdosed. Nicky Mavroleon pointed out that his brother was an experienced drug user. 'Carlos used to tell me that to him it was like having a drink. When he was having a good time he just wanted to get high... but he always knew what he was doing,' he said. Carlos did have a doctorate in drugs and he was far from unused to the vagaries of the local Peshawar heroin.

Also, everyone seems to agree Carlos had not injected for years. Not since 1993 according to his doctor. He had been put off by a friend dying of Aids some years before, his father said. Would he suddenly switch back to syringes? Particularly if, as the police suggest, he had already been smoking the drug.

Could he have committed suicide? Rahimullah Yusufzai saw him shortly before he died and said that though he was shaken by his ordeal at the hands of the intelligence men he was not too worried. A CNN cameraman who bumped into him in a Peshawar street later that day said, with no pun intended, that he 'seemed full of beans, really on a high'.

'He told us how he had been in prison and seemed to think that it was all very amusing,' the cameraman said. 'He had a cutting from a local paper that said that he was a British spy which he said he was going to have framed.'

Everybody who knew him said he was planning to settle down and was as happy as he had ever been. He was to marry in the autumn and was, according to his father, 'devoted' to his fiancée. He had also never entirely lost his Muslim faith and in Islam suicide is as great a sin as it is in Catholicism.

And it seems strange that he would be taking drugs at all. As an old south Asian hand, he must have known that, at least following his arrest, he would almost certainly be under surveillance? Would he have bought the heroin anyway? So would an experienced drug-user make a major mistake using a method he had given up at a time of his life when more than anything he wanted to be clean and happy?

The answer has to be yes. If the suicide scenario is rejected, as it has to be, and the accidental overdose explanation is thrown out too, you are left with nothing but half-baked conspiracy theories. We know that he was tailed throughout his stay in Peshawar and that Green's hotel staff were interrogated by intelligence men both before and after his death. And we know that he was suspected of being a spy. And we can assume the intelligence services, who were tailing him, knew he had bought drugs. But Peshawar breeds conspiracy theories. The basic fact is that there are easier ways to kill someone than making them inject themselves with a deadly syringe. You have to apply Occam's Razor. What is more plausible - an accidental suicide or a plot involving spooks and forced overdoses? In the end, all that you are left with is a grieving family, a brown file on a police chief's desk, a dozen badly typed sheets of paper and the pathologist's 'Heroin poisoning (self)'. The most likely scenario is that a bitterly disappointed Carlos turned to the stand-by which had always helped him when he was feeling low. Relatives say that despite his amazing life he actually had very low self-esteem. The heroin was a prop when he felt down.

And that afternoon in Peshawar the disappointment must have been acute. He desperately wanted the assignment to work. To have got the footage from the camps would have made him a media star. He was 40, wanted children, wanted to settle down and wanted some conventional respect from his more conventional peers. And having, in the last few years, watched reporters like Carlos working in Iraq, in Sierra Leone, in half a dozen other such places, I have seen, and felt the sense of heroic difference, the adolescent joy at your distance from the nine-to-five, from the office, from the suits. Heroin gives you that distance, too. If, when he returned to Green's hotel, Carlos momentarily lacked it he wouldn't for long. To start with he would have felt a mellow, sleepy high as the drug triggered the release of dopamine in his brain. It is quite likely that, if he started off smoking the drug, he would welcome the rush of an injection straight into the bloodstream. If you haven't been using the drug for a while the rush is, one regular heroin user tells me, intensified. A wave of contentment overcomes you. Things stop mattering. For Carlos, by the late afternoon of 27 August 1998, as the towers of Peshawar's mosques stretched their shadows across the superheated roofs of the city and the loudspeakers crackled into the Maghreb prayer, nothing mattered at all.

I left Pakistan earlier this year. Every week I get calls from old friends and contacts in Peshawar and Islamabad. Recently, I have been asking if anything new has turned up on Carlos's death. People have forgotten it now, and these days I am offered friendly advice rather than information. 'Let sleeping ghosts lie,' said one police officer I know.

If Carlos has a ghost it is unlikely to be sleeping.