You have been told a pack of lies on the Chicken legs bit but YES Chicken Tikka Masala was invented probably by a Bangladeshi chef in London or chef in Glasgow - origin disputed. It all began with some tomato soup!
Indians had nothing to do with Chicken legs etc. The whole thing was invented in UK. Fact! Most Indian meals in the West aren't authentic anyway.
For instance, cows are sacred in India and therefore they would not have created Beef Curry. That is why I shy away from these places, not to mention the Halal restaurants that claim to be Indian but again Halal is Islamic and not Indian - Against Indian religions and culture in India. A Halal Indian Restaurant is an oxymoron i.e. the two don't go together