Every 40 seconds, day and night, a dump truck tips 40 tons of rock into a dry ravine, almost 200 metres deep, on one of the world's most remote islands. Rollers swiftly level the rock, each load sprayed with 1,000 litres of water to help compression, and raise the floor level by almost a metre every 24 hours. This will continue for the next 18 months, while a kilometre away engineers will blast off the entire top of a mountain. The rock will then be left to settle, covered in concrete and will form part of the runway of the long-awaited airport on the island of St Helena. The first plane is due to land in February 2016.
Costing a total of almost 250 million, it will be one of the world's most expensive, controversial and challenging airports ever constructed. It will probably see no more than two flights a week, linking this tiny Atlantic island 2000 kilometres from the African coast with South Africa and Britain. But it will be a lifeline for one of Britain's oldest overseas territories. For the first time since St Helena was discovered by Portuguese sailors 511 years ago, the island will no longer have to rely on ships to reach the outside world.
Napoleon, of course, arrived by sea. Almost 200 years ago, the captive emperor was brought here aboard a British warship to begin his six-year exile. With a small entourage of generals, aides and servants who loyally stuck by him after his defeat at Waterloo, Napoleon, pacing the deck, saw the gloomy spectacle that has greeted every sailor approaching St Helena - vast, inhospitable, granite cliffs rising up out of the deep, swirled in mist and challenging anyone to find a landing place.
There is just one - a narrow gully, hemmed in by mountains, that leads down to the sea. This is Jamestown, the picturesque little capital, where Napoleon was brought ashore in October 1815, never to leave the island alive. He did finally depart, 19 years after his death in 1821. Queen Victoria, in a goodwill gesture to France, bought Napoleon's house and grave site with her own money and sold it to Napoleon III, and in 1840 a French warship and military escort arrived to exhume the dead emperor's body. Napoleon was taken back to Paris and re-interred in Les Invalides. A French honorary consul, the only Frenchman on the island, has wonderfully restored the buildings and the furniture so that it looks exactly as it did the day the sick emperor died of stomach cancer.
St Helena has never forgotten Napoleon. Indeed, his exile here is virtually the only reason most people have ever heard of this tiny island. But St Helena was once the crossroads of the world. Situated at a strategic point on the long sea voyage from India, every British ship sailing round the tip of Africa was blown here by the prevailing winds. Ships took on water, fruit, food and fresh crews. Here they put in for repairs, picked up news from England and passed other ships setting off for America laden down with their gruesome cargo of slaves. At the start of the 18th century, three ships a day arrived at Jamestown.
Now there is only one - a British government vessel that goes back and forth from Cape Town to St Helena and then on to Ascension, another British island 1000 km to the north-west that hosts the largest US runway outside America and is the vital staging post on the air route from Britain to the Falklands. The supply vessel brings not only passengers - tourists, British administrators and St Helenians ("Saints" as they are known) returning home - but everything St Helena needs: cars, food, medicines, farm animals, clothes, pots, pans, nails, furniture, cement and every article essential to modern life.
But the Royal Mail ship is getting old and will soon be scrapped. It is also too slow for the modern world: it takes five days to reach Cape Town, and no investor is willing to put money into this remote island's economy if it takes so long to get there. For almost 60 years there has been talk of building an airport, but the cost was always a disincentive. Finally Britain's last Labour government decided to go ahead. But it soon got cold feet because of the cost. The promised airport was put on indefinte "pause". St Helena, long used to being badly treated by its British rulers (which for 160 years was the former British East India Company), settled back into stagnation and gloom.
Now the airport is going ahead. It is the biggest construction project ever undertaken by the South African contractors: every piece of machinery and every component has to be brought in by ship. Before the builders could even reach the mountain top where the runway will be, they had first to carve out a road on the side of the precipitous cliffs to reach the interior.
Britain's plan is that the island should be self-sufficient when the airport opens and tourists start to arrive. But there are huge challenges. The biggest is to change the mistrust that exists between the islanders and the small British administration based in an antiquated building known as the "Castle". There is a culture of dependency on St Helena. For hundreds of years, Britain used the island simply as a fortress and naval base in the Atlantic. But as ships stopped calling here, the economy declined. The Saints began to emigrate. There were few jobs around. The only local industry - making bags out of locally grown flax - stopped when Britain's Post Office started using nylon mailbags instead. Those people left - now no more than 4,200 - are often elderly and depend on British government subsidies. Wages are low, averaging only around 6,000 a year.
St Helena is one of 14 British overseas territories, former colonies that are too small or too poor ever to become independent. Britain is now determined to get things moving again, ready for the airport. Enterprise Saint Helena has been set up to offer help and incentives for small businesses, often no more than one or two people, in traditional occupations such fishing and agriculture as well as small high-tech and craft industries. At the same time, Britain is pouring in money to upgrade the rather low-quality hospital (all seriously sick people have to be evacuated on the ship to Cape Town for treatment), the island's only secondary school, the nature trails and other tourist attractions. There is never going to be a market here for mass tourism or people seeking sand and sea - indeed, it is almost impossible to find a beach anywhere on the coast. But there are plenty of richer travellers who would pay to explore St Helena's steep dells with arum lilies, sleepy hamlets with red-roofed houses, the Napoleonic sites and the unique plants, insects and brightly coloured birds that exist only on St Helena. Isolated from the mainland for millions of years, this island has a rich biodiversity. Scientists and botanists arrive from all over the world to study the spiky yellow woodlouse, the wirebird, the St Helena olive, tree ferns, cabbage trees and dozens of other endemic plant species.
To prepare for the tourists, St Helena must move fast to build more hotels, upgrade the precipitous winding roads, open some restaurants and redevelop the Jamestown waterfront with its castle, museum, small cafes and a prison that dates back to 1805 (and now holds eight prisoners). The aim is to attract small eco-friendly hotels. Already a South African company is negotiating to build a small hotel inside an old fort perched high on the rocks next to the famous "Jacob's Ladder" - a vertiginous 699 stone staircase descending straight down the cliff to Jamestown below. A training school has opened to teach young Saints how to cater and cook. A National Trust has been set up to preserve some of the many 18th century buildings, mark out nature trails, replant forests of the rare indiginous St Helena gumwood trees and make Saints more aware of their heritage.
Many Saints are fairly sceptical of all the activity. Some have no wish to see the island change and do not believe the promise of more jobs and better wages. But most admit that without the airport, the island will die. In 20 years the population fell from 6,000 to 3,500 as the more energetic and ambitious Saints left to find work in Ascension, in the Falklands, in South Africa and in Swindon, a British town that boasts a population of more than 1,000 people from this distant island. Some of the emigrants are now returning. The latest census puts the population at 4,200, and some of the missing middle generation is coming home to take advantage of the coming construction boom.
For the moment, the place still has the dreamy feel of a lost world. There are no mobile phones, and the internet arrived only recently. Television came only three years ago, offering English foot ball, BBC news, entertainment and a few other foreign channels. There are two competing enthusiastic but amateur local radio stations on the island and a new weekly newspaper to offer competition to one that is run almost single-handedly by a Swedish immigrant. But most news is transmitted by a friendly wave in the main street, knots of Saints drinking South African beer in traditional pubs, chat in the all-purpose shops and swiftest way all small communities communicate - gossip and rumour. It will all change. When the firstplane touches down, St Helena will be shaken up more than at any time since Napoleon stepped ashore 198 years ago.