Our soldiers aren't in Sierra Leone for the sake of morals or democracy. They are there for the control of diamonds

Behind its propaganda, British foreign policy is undergoing significant changes. The armed intervention in Sierra Leone is a case in point. It is the biggest of its kind since the Falklands war; and its aims are not, as reported, "vague" or "humanitarian" or in support of the United Nations and "a democratically elected government".

A reliable source of what Tony Blair, Geoff Hoon and Robin Cook are up to in West Africa is the Wall Street Journal, the authentic voice of American corporate power. On 22 March, reports the Journal, the US embassy in Freetown called a top-secret meeting of the multinational corporations that control Sierra Leone's diamond mines, the Freetown government and the RUF rebels, whose territory includes the mines. The US and Britain had forced the government into a coalition with the RUF and demanded that Foday Sankoh, the RUF leader, was given immunity from prosecution and made minister for natural resources, meaning diamonds. That his men were then spreading terror by amputating the limbs of children was not a consideration.

In March, Washington changed tack, believing that its chosen man was unreliable. The RUF was told it had to surrender the mines or face an American-backed war. Behind the latest round of fighting and atrocities, says the Journal, was "US and British determination to wrest control of Sierra Leone's rich diamond mining areas from the RUF rebels . . . The key role of mining interests in the fighting is nothing new in Sierra Leone. Rival mining companies, security firms and mercenaries from South Africa, Britain, Belgium, Israel and the former Soviet Union have poured weapons, trainers, fighters and cash into the country. They have backed the government or the rebels in a bid to gain access to the country's high-quality gems."

In 1998, the country's international diamond trade had a market value of £4.2bn, producing jewellery worth an estimated £35bn. The South African-based De Beers company mines 40 per cent of the world's diamonds and has been in Sierra Leone since 1935, when it was given exclusive mining rights by the British. These days, the company's role is indirect and secretive, yet reportedly undiminished, with many of Sierra Leone's diamonds sold for cash and smuggled through Liberia. De Beers has a prominent place in new Labour's Millennium Dome.

Justifying the invasion, Robin Cook wrote in the Sun: "Instability on the other side of the world can lead to fewer jobs in our factories, more drugs on our streets and more asylum-seekers at our door." In other words, the paratroopers are really guarding British jobs and keeping out dreadful refugees. That gives some idea of the regard in which the Foreign Office holds the intelligence of the British public.

Cook's appeal to racism and job insecurity via Rupert Murdoch coincided with the Defence Secretary's announcement that he was lavishing £5bn on military equipment - soon after the government had said it could not afford more than 75p a week extra for pensioners. More than £3.5bn is to be spent on a new European airbus for use by British troops on military adventures abroad. Adventures like Sierra Leone, which is seen as a model for future interventions.

This policy was promised in the Strategic Defence Review overseen by George Robertson. "We have a responsibility to act as a force for good in the world," said the review. Few questions were asked by journalists, or pressed by MPs. At the time of the Nato attack on Yugoslavia, Robertson spoke of British policy "crossing the Rubicon". In Washington, with Clinton nodding beside him, Blair told the world to watch out: British "moralism" was back.

The British military establishment has always prided itself on its efficiency in putting down natives on behalf of "British interests". The pretence of moralism is meant to revive the respectability of the great mission of imperialism; Cecil Rhodes, plunderer and land thief, used the same term. With gunboats off West Africa, Britain is back on the beat. The difference now is that it is also there on Washington's behalf, Congress having a disconcerting habit of constraining the executive here and there from deploying military forces - something unimagined in Blair's domain.

At the Foreign Office and the Ministry of Defence the new project is described, in Chatham House jargon, as Britain "building a purposeful bridge" between European power and American superpower in their relations with the rest of the world. The buzz term is "nexus power".

Watch where the paras and the SAS and the gunboats are next sited. Zimbabwe? What worries the British is that most rural Zimbabweans, having had their expectations raised by President Robert Mugabe's rhetoric, will join a genuine mass land-reform movement that will be outside his and his goons' control; and that similar movements will spread to South Africa and Namibia and even Kenya, all of which are treasure troves for British capital.

In South Africa, where British multinationals are the largest foreign investors and a powerful influence on the ANC's neoliberal policies, the land issue is stirring in a country where many people are poorer than they were under apartheid, and 80 per cent of the prime land is controlled by a small minority of whites: an injustice enshrined in the Mandela-era constitution. Like Mugabe, President Thabo Mbeki may find that he cannot control his people, even with an army still mostly white-led and equipped largely by the British arms industry. What is certain is that Blair's boys and boats are now ready. Cecil Rhodes would approve.