The use of L1 in Teaching English as a Second Language contexts is a ubiquitous but haphazard pedagogical practice in Sri Lanka. This thesis examines whether the use of L1 (Sinhala) could be validated across high, intermediate, and low learner proficiency levels in English. Sociolinguistically, the complex ontological and epistemological milieu of ESL in Sri Lanka granted this thesis an entree for scrutinizing the evolution of resistance to English in the undergraduate participants. The findings of pilot studies validated the expulsion of high proficiency learners from the procedures of L1 integration. Conversely a significant % mean increase across the intermediate and the low proficiency learners was revealed under the Sinhala Gloss (SG) condition. The mean comparison for both populations was equal and low for No Gloss (NG) and English Gloss (EG) conditions resulting in the gloss condition performance indicator NG = EG > SG. Scaffolding these findings to pedagogy, the study confines integrating L1 to skill development in lexical comprehension mechanisms in low and intermediate proficiency learners and discusses developing L2 inferring skills in the high proficiency learners."