The British presence in India began through trade. Men like Robert Clive of the British East India Company combined military prowess with a ruthless ambition and became fabulously wealthy. With wealth came power, and traders took control of huge swathes of India.
It acquired control of Bengal on the India in 1757, and, as the company was an agent of British imperialism, its shareholders were able to influence British policy there. This eventually led to government intervention.