This PhD by publication is underpinned by three journal articles which together explore attitudes towards using the students’ L1 in various English language teaching contexts. Publication One investigates a dual-language instructional technique used with secondary school students in a CLIL context. Publication Two compares the attitudes and practices of EFL teachers towards using the L1, firstly in shared-L1 contexts and secondly in multilingual contexts where students do not share a common L1. Publication Three examines the cognitions of teacher trainers around using the L1 in language teaching and how this issue is dealt with on CELTA programmes. Four research aims are addressed: to explore the attitudes, beliefs and cognitions of educators towards using the L1 in language teaching [Publications 2,3]; to identify the extent to which ELT practitioners view their students as (emerging) bilinguals and the classroom as a bilingual space [Publications 2, 3]; to consider the role of the teaching context in pedagogic decisions around using the L1 in the classroom [Publications 1,2,3]; and to examine the potential role of bilingual instructional perspectives and techniques to enhance language learning [Publications 1,2,3]. Findings point to the continued dominance of the monolingual principle among ELT professionals and the need to revisit some of the taken-for-granted assumptions about best practice in relation to this in language teaching. The study also demonstrates the flexible and often inconsistent positions taken by educators in relation to L1 use in language teaching and the influence of the particular teaching context on their practices. The role of teacher development programmes in exploring this issue in a considered and reflective way is also identified. Findings highlight the value of exploiting the bi/multilingual skills of both teachers and students and of embracing bilingual perspectives to facilitate learning.