“The term curry itself isn’t really used in India, except as a term appropriated by the British to generically categorize a large set of different soup/stew preparations ubiquitous in India and nearly always containing ginger, garlic, onion, turmeric, chile, and oil (except in communities which eat neither onion or garlic, of course) and which must have seemed all the same to the British, being all yellow/red, oily, spicy/aromatic, and too pungent to taste anyway”. (Author:Brent Thompson/Chile-Heads mailing list posting)

In terms of modern history the popularity of curry in the UK and elsewhere is surely linked to the rise of the “Indian” restaurant. Yet the majority of UK restaurants are run by people of Bangladeshi, not Indian, origin. Their influences are obviously from Bangladesh but the restaurateurs have in turn been influenced by the likes and dislikes of their customers. They have modified dishes and incorporated new dishes from other areas of the sub-continent.
What the British call “curry” is now an international dish recognised on every continent. Dishes develop and change according to a host of new influences. For instance, the most popular curry in UK restaurants is Chicken Tikka Masala. Many people would think of it as a typical Indian dish. But it is actually a restaurant invention created in the UK by Bangladeshi restaurateurs. A true hybrid and a recent chapter in the long history of curry.(Source: A Brief History of Curry by David Smith)

So-called “Curry Powder,” denoting a mixture of spices sold commercially, is largely a Western notion, dating to the 18th century. Such mixtures are commonly thought to have first been been prepared by Indian merchants for sale to members of the British Colonial government and army returning England.