There is a story that is commonly told in Britain that the colonisation of India - as horrible as it may have been - was not of any major economic benefit to Britain itself. If anything, the administration of India was a cost to Britain. So the fact that the empire was sustained for so long - the story goes - was a gesture of Britain’s benevolence.

New research by the renowned economist Utsa Patnaik - just published by Columbia University Press - deals a crushing blow to this narrative. Drawing on nearly two centuries of detailed data on tax and trade, Patnaik calculated that Britain drained a total of nearly $45 trillion from India during the period 1765 to 1938.

It’s a staggering sum. For perspective, $45 trillion is 17 times more than the total annual gross domestic product of the United Kingdom today.

It happened through the trade system. Prior to the colonial period, Britain bought goods like textiles and rice from Indian producers and paid for them in the normal way - mostly with silver - as they did with any other country. But something changed in 1765, shortly after the East India Company took control of the subcontinent and established a monopoly over Indian trade.

Here’s how it worked. The East India Company began collecting taxes in India, and then cleverly used a portion of those revenues (about a third) to fund the purchase of Indian goods for British use. In other words, instead of paying for Indian goods out of their own pocket, British traders acquired them for free, “buying” from peasants and weavers using money that had just been taken from them.

It was a scam - theft on a grand scale. Yet most Indians were unaware of what was going on because the agent who collected the taxes was not the same as the one who showed up to buy their goods.

Had it been the same person, they surely would have smelled a rat.

Some of the stolen goods were consumed in Britain, and the rest were re-exported elsewhere. The re-export system allowed Britain to finance a flow of imports from Europe, including strategic materials like iron, tar and timber, which were essential to Britain’s industrialisation. Indeed, the Industrial Revolution depended in large part on this systematic theft from India.

On top of this, the British were able to sell the stolen goods to other countries for much more than they “bought” them for in the first place, pocketing not only 100 percent of the original value of the goods but also the markup.