Anton Balasingham, theoretician and political advisor of Sri Lanka's Tamil Tiger rebels, passed away Thursday in London, rebel sources said. Daya Master, the Liberation Tigers of Tamil Eelam (LTTE) official in the rebel held Kilinochchi district in the north of the island said Balasingham, 66, had died in a London hospital. Balasingham was suffering from cancer for a long time and had stayed away from his LTTE work due to ill health for a long time. He has acted as the LTTE's chief negotiator in the peace negotiations with the Sri Lankan government aimed at ending the country's drawn-out separatist armed conflict. The London based theoretician visited Colombo for talks with the government in 1990 and then led the LTTE delegation in all six rounds of peace talks between September 2002 and March 2003. He also led the rebel delegation in the Geneva peace talks held in February this year. He was the adviser to the reclusive rebel leader Velupillai Prabakaran and was known for his moderate thinking in the rebel organization.