And there is the Khyber Railway, a further pleasure. Built fifty years ago at great cost, it is an engineering marvel. It has thirty-four tunnels, ninety-two bridges and culverts, and climbs to 3600 feet. The train is well guarded: on bluffs above the track, in little garrisons and pillboxes, the Khyber Rifles stand sentry duty, staring blankly at the plummeting blue black ravines on Afghanistan's inhospitable edge.

There is only one train a week on the Khyber Railway, and practically all the passengers are what the Pakistanis refer to as 'tribal people', the Kuki, Malikdin, Kambar, and Zakka Khel, indistinguishable in their rags. They use the train for their weekly visit to the bazaar in Peshawar. It is an outing for them, this day in town, so the platform at Landi Kotal station in the Khyber Pass is mobbed with excited tribesmen tramping up and down in their bare feet, waiting for the train to start. I found a seat in the last car and watched a tribesman, who was almost certainly insane, quarrelling on the platform with some beggars. A beggar would limp over to a waiting family and stick his hand out. The lunatic would then rush up to the beggar and scream at him. Some of the beggars ignored him; one hit back, rather lazily slapping him until a policeman intervened.

The lunatic was old. He had a long beard, an army surplus overcoat, and wore sandals cut from rubber tyres. He squawked at the policeman and boarded the train, choosing a seat very near me. He began to sing. This amused the passengers. He sang louder. Beggars had been passing through the car – lepers, blind men led by little boys, men on crutches – the usual parade of rural unfortunates. They shuffled from one end of the car to the other, moaning. The passengers watched them with some interest, but no one gave them anything. The beggars carried tin cans of dry bread crusts. The lunatic mocked them: he made faces at a blind man; he screamed at a leper. The passengers laughed; the beggars passed on. A one-armed man boarded. He stood flourishing his good arm, presenting his stump, a four-inch bone at his shoulder.

'Allah is great! Look, my arm is missing! Give something to my wounded self!'

'Go away, you stupid man!' shouted the lunatic.

'Please give,' said the one-armed man. He started down the car.

'Go away, stupid! We don't want you here!' The lunatic rose to torment the man, and as he did so the man pounced on him and gave him a terrific wallop on the side of his head, sending him reeling into his seat. When the one-armed man left, the lunatic resumed his singing. But now he had no listeners.

The translation of this dialogue was provided by two men sitting near me, Mr Haq and Mr Massan. Mr Haq, a man of about sixty-five, was a lawyer from Lahore. Mr Hassan, from Peshawar, was his friend. They had just come from the border where, Mr Haq said, 'We were making certain inquiries.'

'You will like Peshawar,' said Mr Hassan. 'It is a nice little town.'

'I would like to interrupt my learned friend to say that he does not know what he is talking,' said Mr Haq. 'I am an old man – I know what I am talking. Peshawar is not a nice town at all. It was, yes, but not now. The Afghanistan government and the Russians want to capture it. It was the Russians and Indians who took a piece of Pakistan away, what they are calling Bangladesh. Well. Peshawar was once great some time back. It is full of history, but I don't know what is going to happen to us.'

The train had started, the lunatic was now tormenting a small boy who appeared to be travelling alone, the tribesmen – all elbows – were at the windows. It was an odd trip: one moment the car would be filled with sunshine, and outside the head of the valley shifted to a view of a tumbling stone gorge; the next moment we would be in darkness. There are three miles of tunnels on the Khyber Railway, and as there were no lights on the train, we travelled those three miles in the dark.

'I would like very much to talk to you,' said Mr Haq. 'You have been to Kabul. You can tell me: is it safe there?'

I told him I had seen a lot of soldiers, but I supposed they were around because of the military coup. Afghanistan was ruled by decree.

'Well, I have a problem, and I am an old man, so I need some advice.'

The problem was this: a Pakistani boy, a distant relative of Mr Haq's, had been arrested in Kabul. What with difficulties in obtaining foreign currency and the impossibility of travelling to India, the only place holiday-minded Pakistanis go to is Afghanistan. Mr Haq thought the boy had been arrested for having hashish, and he had been asked whether he would go to Kabul to see if he could get the boy released. He wasn't sure he wanted to go.

'You tell me. You make the decision.'

I told him he should put the matter in the hands of the Pakistani embassy in Kabul.

'Officially we have diplomatic relations, but everyone knows we have no diplomatic relations. I cannot do.'

'Then you have to go.'

'What if they arrest me?'

'Why would they do that?'

'They might think I'm a spy,' said Mr Haq. 'We are almost at war with Afghanistan over the Pakhtoonistan issue.'

The Pakhtoonistan issue was a few villages of armed Pathan tribesmen, supported by Russia and Afghanistan, who were threatening to secede from Pakistan, declare a new state, and, deriving their income from dried fruit, become a sovereign power; the liberated warriors would then compete in the world market of raisins and prunes.

'My advice is don't go,' I said.

'How can you say that! What about the boy? He is a relative – his family is very worried. I wish,' said Mr Haq, 'toask you one further question. Do you know Kabul's jail?'

I said I didn't, but I had seen Kabul's insane asylum and did not find it encouraging.

'Kabul's jail. Listen, I will tell you. It was built in the year 1626 by King Babar. Well, they call it a jail, but it is a number of holes in the ground, like deep wells. They put the prisoners in. At night they cover them up with lids. That is the truth. They do not give food. The boy might be dead. I don't know what I should do.'

He fretted in Urdu with Mr Hassan, while I snapped pictures of the ravines. We ducked into tunnels, emerging through spurs to reversing stations; above us were fortified towers and stone emplacements, bright in the midafternoon sun. It seems an impossible journey for a train. The 132-Down teeters on the cliff sides, breathing heavily, and when there is nothing ahead but air and a vertical rock face the train swerves into the mountain. Plunging through a cave, it dislodges bats from the ceiling, which the tribesmen at the windows swat with their sticks. Then into the sunlight again, past the fort at Ali Masjid, balancing on a high peak, and an hour later, after twenty sharp reverses, moves on a gentler slope in the neighbourhood of Jamrud. Above Jamrud is its bulky fort, with walls ten feet thick and its hornworks facing Afghanistan.

Some tribesmen got out at Jamrud, moving Mr Haq to the observation: 'We do what we can with them, and they are coming right up.'

He fell silent again and did not speak until we were travelling through the outskirts of Peshawar, beside a road of clopping tongas and beeping jalopies. Here, it was flat and green, the palms were high; it was probably hotter than Kabul had been, but so much green shade made it seem cool. Behind us the sun had dropped low, and the peaks of the Khyber Pass were mauve in a lilac haze so lovely it looked scented. Mr Haq said he had business here – 'I have to solve my great worry.'

'But let us meet later,' he said at Peshawar Cantonment Station. 'I will not trouble you with my problems. We will have tea and talk about matters of world interest.'

Peshawar is a pretty town. I would gladly move there, settle down on a verandah, and grow old watching sunsets in the Khyber Pass. Peshawar's widely spaced mansions, all excellent examples of Anglo-Muslim Gothic, are spread along broad sleepy roads under cool trees: just the place to recover from the hideous experience of Kabul. You hail a tonga at the station and ride to the hotel, where on the verandah the chairs have swing-out extensions for you to prop up your legs and get the blood circulating. A nimble waiter brings a large bottle of Murree Export Lager. The hotel is empty; the other guests have risked a punishing journey to Swat in hopes of being received by His Highness the Wali. You sleep soundly under a tent of mosquito net and are awakened by the fluting of birds for an English breakfast that begins with porridge and ends with a kidney. Afterwards a tonga to the museum.