British factories brought in raw materials from India, which were converted into finished products in British factories and then sold back to countries in the British Empire.
This created many jobs [eg. dock workers, factory workers, shopkeepers] and British businesses made lots of money.
The Indian Army fought bravely and decisively on Britain's side in the First and Second worldwars.
Indian tea became a popular drink in Britain and Indian food became very common.
Indian words such as 'bangle' and 'shampoo' became commonly used and buildings [eg. Royal Pavilion, Brighton] were built in an Indian style.