The crisis in UK mathematics education, both in schools and universities, has been widely reported. Currently, 24% of full-time mathematics teachers in English secondary education have "weak" or "nil" qualifications in the subject, 31% of secondary mathematics teachers are now over the age of 50, and it is estimated that England alone is short of 3500 qualified mathematics teachers. Furthermore, studies suggest that UK mathematics undergraduates often lack confidence in several key skills essential for teaching, and the availability of attractive careers for mathematics graduates impacts upon the numbers entering the profession, thus risking a spiral of decline. This paper recounts the development of a unit of study in the Faculty of Mathematical Studies at the University of Southampton, England, in conjunction with a new national initiative entitled the "Undergraduate Ambassadors Scheme" (UAS). This aims to address the crisis in UK mathematics education through the training and placement of final year undergraduates as teaching assistants in local schools, with a view to promoting mathematics as a university choice to the broadest possible constituency, whilst simultaneously developing those key skills in which undergraduates regularly feel least confident, and facilitating an insight into teaching as a career option. The paper also provides a detailed evaluation of this new initiative, together with the recent comments of students who, having completed the UAS unit, have progressed subsequently to postgraduate teacher education.