The people of Britain have, in their brains and on their tongues, an asset worth billions of pounds across the globe: the English language. And new research has shown that it is not only the rich and powerful who benefit from mastery of the first truly international language: from Nigeria to Bangladesh, even humble carpenters and plumbers who speak a smattering of English are upwards of 30 per cent richer than their competitors who do not.

English is big business indeed, and not just for the world’s leaders, statesmen and diplomats, all of whom are routinely required to master it. Millions of children on every continent now spend years studying the language. English has become the passport to wealth and opportunity, an essential requirement for almost every profession and the means by which a third of all internet communication is conducted.

Planes take off and land in English. UN officials negotiate war and peace in English. Protesters in distant countries scrawl their demands on placards in English for the world’s cameras. It is the language used to pioneer the latest research, open the Olympic Games, broadcast the rescue of the Chilean miners and splash WikiLeaks secrets across the world’s television screens.

English, which has been steadily gaining ground since the Second World War, is nowadays being embraced by entire countries and regions. The elites of Egypt, Syria and Lebanon have dumped French in favour of English. India has reversed its former campaign against the language of its colonial rulers, and millions of Indian parents are enrolling their children in English-language schools – the surest route to joining the growing Anglophone middle-class. Since 2005, India has had the world’s largest English-speaking population, with far many more people using the language than before independence. Rwanda, in a move dictated as much by regional economics as post-genocide politics, has decreed a wholesale switch to English as its medium of instruction. And China is about to launch a colossal programme to tackle one of the few remaining obstacles to its breakneck expansion: a paucity of English-speakers.

As Britain’s former economic and industrial dominance has faded, its language has become ever more vital to its prosperity. Millions of tourists visit Britain largely because they can understand the language (if not always the native speakers). Language schools are booming. Universities earn millions from China and other nations keen to educate their elites in English. The BBC World Service and the British Council are arguably greater agents of global influence than the country’s entire diplomatic corps. And one reason for London’s pre-eminence as a centre for diplomacy and global communications is that the native language is English, which has by now almost entirely replaced French as the language of diplomacy.

The latest statistics attest to the growing pervasiveness of English. Last year the British Council taught English to 279,000 learners, in 80 centres spread across 40 countries, and delivered 2.2 million exams to 1.6 million individuals worldwide. This work earned an income of £27 million – a 20 per cent increase on 2008 – and delivered £47 million in exports earnings for UK exam boards. In 2008-09, some 10.5 million unique visitors accessed the British Council’s free access global learner websites, which include dedicated Arabic and Chinese websites; meanwhile, downloads from teacher websites reached more than 21 million students. And in the 20 years since it was launched, the International English Language Testing System (IELTS) has been taken by more than 6 million people across 135 countries; today, roughly 1.4 million candidates sit the test each year.

What has not been documented until now, however, is the real value of English to those who learn it. A poll commissioned  by Euromonitor, an international market research company, across five developing countries – Cameroon, Nigeria, Rwanda, Bangladesh and Pakistan – found clear evidence that people with English-language skills, including those living in remote villages, typically earn at least 30 per cent more than non-English speakers. Senior managers in Bangladesh who speak English earn $960 a month, compared to $720 for their colleagues who do not. English-speaking carpenters in Pakistan and Nigeria can, respectively, expect to bring in just under and well over twice what they would otherwise earn if they only spoke their native tongues. For receptionists in Rwanda the premium is even higher: $270 per month, against a basic wage of $110.

Euromonitor’s poll did not give reasons for the huge economic advantages enjoyed by these English-speaking workers. But in all five countries more than half the companies interviewed reported that their workforce was required to speak English to at least an intermediate level. As a result, the demand for English is growing at an extraordinary rate: in Bangladesh, where only 18 per cent of the population can speak English, the figure is expected to rise to 25 per cent over the next five years; in Nigeria, where 54 per cent can, the proportion will rise to 66 per cent.

English is making countries richer overall, too. Foreign direct investment (FDI) is hugely influenced by the ability to understand its recipients; among the five sampled countries, FDI is greatest where English is strongest, in Nigeria and Pakistan. English even plays an important role in Africa’s relations with China, as both sides race to find a common language as Chinese investment pours in. This helps to explain why China is attempting to teach English to almost a billion of its citizens, and why Rwanda, with considerable help from the British Council, is now teaching all of its schoolchildren in English and trying to bolster knowledge of the language by 10 per cent each year.

Britain no longer owns its language. Indeed, most people no longer associate English mainly with England. Nonetheless, subtly, in thousands of phrases, sayings and associations, the English language continues to spread both knowledge of its birthplace and familiarity with the British ‘mindset’. And Britain is still making a far greater effort to spread its language than any other Anglophone country. America doesn’t bother. Australia, a lively competitor, does not yet have the reach or resources of the British Council and hundreds of other, private, British providers.

As Euromonitor shows, demand for English is growing exponentially. If Britain capitalises on this opportunity – an opportunity cruelly denied nowadays to the French – it could earn more from its language than from any other export manufactured in these islands.