This article is a narrative case study of language provision for trainee mathematics teachers on a one-year initial teacher training course: a Postgraduate Certificate in Education in London, England. It draws on Heugh's (2018) (Conclusion: Multilingualism, Diversity and Equitable Learning: Towards crossing the 'Abyss'. in The Multilingual Edge of Education 2018 (pp 341-367) Palgrave MacMillan) description of Functional Multilingualism; Muscovitch's (2015) Academic Literacy in Mathematics for English learners in The Journal of Mathematical Behaviour, 40, 43-62) to intertwine the development of professional language repertoires with the praxis of school mathematics pedagogy; and digital multimodal literacies to promote writing, professional language repertoires and critical language awareness. It models practices and tasks designed to improve outcomes in the Postgraduate Certificate in Education course and address the lack of confidence felt by trainee teachers when teaching multilingual classes. These develop safe spaces that allow for sharing of school practicum experiences and is a context for discussion of race literacy and other aspects of diversity and inclusion referred to in the Equalities Act (2010). Drawing on innovation over a four-year period (2017--2021) the case study provides a variety of starting points to develop consistency within the many initial teacher training routes leading to Qualified Teacher Status and for collaboration between schools and Higher Education Institutes during further two years of school-based training required in England before final recognition as a fully qualified teacher.