Indian Cuisine in the UK

The word curry, meaning 'to spice' has been used since the medieval period. Nowadays, a night out in the pub, followed by a curry, is a tradition in many cities.
Great crappy 1970's picture. 

 Ever since the Victorian era, during the British Raj, Britain has been "borrowing" Indian dishes, and then creating Anglo-Indian cuisine to suit the British palate. Back then we came up with kedgeree, Coronation Chicken and mulligatawny soup, all traditional Anglo-Indian dishes, but they are not that popular today. More recently many varieties of Indian curry of which chicken tikka masala and balti are the best known have been popularised. In fact chicken tikka masala is now considered one of Britain's most popular dishes.

A brief history

British cuisine has always been multicultural, a pot pourri of eclectic styles. In ancient times influenced by the Romans and in medieval times the French. When the Frankish Normans invaded, they brought with them the spices of the east: cinnamon, saffron, mace, nutmeg, pepper, ginger. Sugar came to England at that time, and was considered a spice -- rare and expensive. Before the arrival of cane sugars, honey and fruit juices were the only sweeteners.

The few Medieval cookery books that remain record dishes that use every spice in the larder, and chefs across Europe saw their task to be the almost alchemical transformation of raw ingredients into something entirely new (for centuries the English aristocracy ate French food) which they felt distinguished them from the peasants.

Let them eat cake" is the traditional translation of the French phrase "Qu'ils mangent de la brioche", supposedly spoken by "a great princess" upon learning that the peasants had no bread. Since  brioche was a luxury bread enriched with butter and eggs, the quote would reflect the princess's disregard for the peasants, or her poor understanding of their situation.
While the phrase is commonly attributed to Queen Marie Antoinette, there is no record of her having said it. It appears in book six of Jean-Jacques Rousseau's Confessions, his autobiography whose first six books were written in 1765, when Marie Antoinette was nine years of age.

During Victorian times good old British stodge mixed with exotic spices from all over the Empire. And today despite being part of Europe we've kept up our links with the countries of the former British Empire, now united under the Commonwealth.
One of the benefits of having an empire is that we did learn quite a bit from the colonies. From East Asia (China) we adopted tea (and exported the habit to India), and from India we adopted curry-style spicing, we even developed a line of spicy sauces including ketchup, mint sauce, Worcestershire sauce and devilled sauce to indulge these tastes. Today it would be fair to say that curry has become a national dish.

Unfortunately a great deal of damage was done to British cuisine during the two world wars. Britain is an island and supplies of many goods became short. The war effort used up goods and services and so less were left over for private people to consume. Ships importing food stuffs had to travel in convoys and so they could make fewer journeys. During the second world war food rationing began in January 1940 and was lifted only gradually after the war.

The British tradition of stews, pies and breads, according to the taste buds of the rest of the world, went into terminal decline. What was best in England was only that which showed the influence of France, and so English food let itself become a gastronomic joke and the French art of Nouvell Cuisine was adopted.

So from what I've goggled and still goggling, Indian food has been around in the way of Curry Powders for centuries via the spice traders.

A more modern day Indian cuisine was introduced to the UK in 1940's with the influx of the Indian works in the Jute Factories and by the 1960/70's the Indian "take out restaurants" made their first proper appearance. 
But the Curry House's have been in Brittan since the 1780's.