Perhaps you should read up on yours. The Tamil population may have been increased by immigration during the time of Empire, but Tamils have established there for a lot longer. Archeological evidence in the form of ceramic shards and stones bearing tamil script dating back to hundreds of years BC shows that Tamils have lived in Northern Sri Lanka since at least then...
No, I am very familiar with them since I had both Sinhalese and Tamil in my factory Crews and spoke at length with them on this very subject, My foreman (Sinhalese) lost his Older Brother in the conflict..