In the 19th century, India emerged as a major market for British manufactures and supplied food grains and raw materials.
Opium from India was sold in China, enabling Britain’s triangular trade with China. Railways were a major area of investment of capital.
Britain’s international balance of payments deficit was handled by the foreign exchange got from Indian exports.
British shipping grew in leaps and bounds on the back of its control over India’s coastal and international trade.
England was particularly keen on the Indian empires as it provided a market for cotton goods; it controlled the trade of the Far East with her export surplus (opium) with China. The Home Charges (India’s payments for receiving “good” administration from Britain) and the interest payments on the Indian Public Debt were important in financing Britain’s balance of payments deficit.
The projection of India as the brightest jewel in the Britain crown played an important role in the ideology of imperialism. The Britain ruling classes were able to keep their political power intact even when it was being driven with class conflict. Thus, the pride and glory underlying the slogan of the sun never sets on the British Empire were used to keep workers contented on whose slum dwellings the sun seldom shone in real life.
India also played a crucial role in one other, often ignored, aspect. India bore the entire cost of its own conquest. India paid for the railways, education, and modern legal system, development of irrigation and detailed penetration of administration into the countryside.
Lastly once the struggle for the division of the world became intense after 1870 India was the chief gendarme of British imperialism. She provided both the material and the human resources for its expansion and maintenance. Afghanistan, Central Asia, Tibet, the Persian Gulf area, Eastern Africa, Egypt, Sudan, Burma, China and to some extent even South Africa was brought or kept within the British sphere of influence by virtue of Indian men and money.
The Britain Indian army was the only large scale army contingent available to Britain. It is therefore not a surprise that the British Empire in Asia and Africa collapsed once Britain lost control over the Indian army and finances.