After that, everyone wants to be our friend for life. There’s a handsome, earnest young man who starts showing us photographs of his family, and his qualification certificate in “sales electronic”. His bachelor status, as well as his proficiency in sales electronic, soon attracts the attention of two giggling teenage girls from Udaipur, and they start to flutter their kohl-rimmed eyelashes at him furiously.

Then there’s the creaking of old, tired metal, a groaning of pistons and a straining of couplings, and . . . we’re off! The air conditioning kicks in — a breeze through the open windows, and indeed the open doorways. The doors have, sensibly, been removed long ago, so people can hop on and off when they please, Routemaster-style. On the minus side, the loos: you won’t want to use them.

Seriously. Go beforehand. If you’ve read Cormac McCarthy’s Blood Meridian, you’ll remember — indeed, you will never, ever forget — the horrific last scene, which takes place in an outdoor privy. This is worse. Don’t go there.

The train is slow, the day is hot, the cicadas chirrup from the brush and the dirty steam drifts past. At the tiny villages en route, called things like Polat and Lehamli, with whitewashed station houses covered in bougainvillea, the girls hop off to buy vegetable pakoras and bananas, and share them round the whole carriage.

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The station monkeys are shyer and notably better behaved than their city cousins. Quite often, while the old engine sits and puffs away gently, getting her breath back for the next bit of ascent, the driver walks back down the train to say hello to everyone aboard. This doesn’t improve the journey time, but nobody is bothered. It’s all very different to the 7.48 from Sevenoaks.

As we climb higher into the hills, the dusty, enervating air begins to cool and the view becomes more magnificent with every bridge and bend. To the northwest lies the vast emptiness of the Thar desert, and to the southwest the Great Rann of Kutch, which sounds like something out of a children’s book. (“The Great Rann of Kutch was very fat, and had 18 wives, and was far too fond of butter...”)

Children whoop every time we pass through another tunnel and emerge, blinking, into the sunshine again. And the hills grow more thickly forested as we rise. Some geologists reckon that the Aravalli Hills are the oldest on earth, the worn-down, weather-beaten stumps of once mighty mountains that out-topped the Himalayas.

You can easily imagine that they are the setting for Kipling’s The Jungle Book. Wasn’t Bagheera once a captive panther in a cage, in the palace of Udaipur? And when he escaped, might it not have been to these ancient, forested hills?

The romantic traveller can certainly imagine so. There are still leopards in these hills, as well as brilliant yellow butterflies dancing over the tops of the acacias, and lonely goatherds waving shyly beside the railway tracks.

The train creeps onward over old bridges, with precipices dropping away to the right and gorgeous Shangri-la valleys dotted with limpid green rock pools. We finally emerge onto a moorland summit, 2,158ft above the plains, to find a proudly uniformed signalman even here, waving a green flag as we inch past. The landscape is oddly reminiscent of the Brecon Beacons, only hotter, with lapwings and plovers and little moorland pools.

There’s an unscheduled stop just after the lovely village of Khamli Ghat, as a dog is asleep in the middle of the track. The train sits and puffs indignantly. The dog doesn’t stir. The driver pulls his whistle cord. Very slowly, the dog gets to his feet, shakes himself and wanders off. At the top of a rise, he looks back and watches us creep past with an Eeyore-like expression, one ear sardonically cocked. “Trains? Don’t give me trains.”

At last, we arrive at Deogarh station, say farewell to all our new friends and find our driver. Then it’s off for a couple of nights at Deogarh Mahal, a fantastic, labyrinthine palace that overlooks a lake, and a candelit dinner on the rooftop terrace.

A day or two later we talked to Nandi, 22, a maharajah’s son. Tall, broad-shouldered and handsomely mustachioed, he seemed to radiate seven centuries of Rajput breeding.

Of all the things the British did for India, surely the trains were one of the least mixed blessings? Yes, he agreed. India without trains was impossible to imagine. There was other stuff, too. We enumerated the civil service, irrigation and the English language, while carefully steering round 1857, Amritsar and partition.

Finally, he gave us the best verdict on the Raj I’ve heard — worthy of Kipling in its irony. He brought his huge hands together, steepled his fingers, touched his fingertips to his chin and, smiling gently, said: “I think you could say the British gave us everything we needed to get rid of them.”

Christopher Hart travelled as a guest of wildfrontiers.co.uk

Travel details: Wild Frontiers (020 7736 3968, wildfrontiers.co.uk ) can organise tailor-made trips throughout India, with two weeks in Rajasthan starting at about £2,600pp. The price includes the Marwar Junction to Deogarh rail trip, a stay in the Deogarh Mahal Palace (deogarhmahal.com ; doubles from £80), accommodation in Raj palace hotels and a luxury tented camp, flights from Heathrow to Delhi and a car and driver. Or try Pettitts (01892 515966, pettitts.co.uk ).

Trains run from Marwar Junction to Deogarh daily; tickets cost about 20p if bought locally. It is easier to include the journey as part of a trip with a car and driver, as above. Or contact SD Enterprises (020 8903 3411, indiarail.co.uk ), which sells seven-day unlimited-use rail passes for £103pp.

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