I have provided lot of references in the AFD page. Please find it there rather looking it in the talk page.
 http://www.island.lk/2002/01/27/featur01.html
 http://www.island.lk/2010/05/11/news29.html
 http://www.island.lk/2003/02/22/satmag04.html
 http://www.dailynews.lk/2004/10/13/artscop12.html
 http://www.dailynews.lk/2012/07/16/fea03.asp

 You can find lot of books in here
 https://www.google.com/search?q=mahawamsa+rajarata+king&ie;=utf-8&oe;=utf-8&aq;=t&rls;=org.mozilla:en-US:official&client;=firefox-a#q=rajarata+%2B+kingdom&hl;=en&client;=firefox-a&tbo;=d&rls;=org.mozilla:en-US:official&tbm;=bks&source;=lnms&sa;=X&ei;=WgKmUNnBEOaLjAKAs4HQBQ&ved;=0CAkQ_AUoAA&bav;=on.2,or.r_gc.r_pw.r_cp.r_qf.&fp;=f316b7445f503d95&bpcl;=38625945&biw;=1356&bih;=583

Kind request to Obi2canibe
I haven't say it was latest 18 centuries. Anyway if it is not true please correct it rather asking to delete the page.