it seems Tamilians(Chola, Pandyans) were regularly raiding Sinhalese kingdoms right from time immemorial and British used this to divide and rule Sri Lanka when they annexed SL. So Sinhalese were upset and came out with all sorts of stupid policies. Unfortunately for SL there was no Gandhi in their midst and things went from bad to worse. So just like how in India Britishers exploited hindu-muslim rivalry for their own political gains, they exploited that issue too in SL. That is the history. It is complex and needs to be solved with care.