In the present thesis the impact of a language learner development scheme to promote learner autonomy in mostly L1 English-speaking students in a German Language Degree Course at the University of Liverpool is examined. For the purpose of the investigation, a new, theoretically motivated process model of learner autonomy is put forward. In order to investigate the claimed effects identified from the model, a guided independent language learning programme based on portfolio learning, was developed and established as an assessed part of the German Course. The aim of the Scheme was to raise awareness of the language learning process and thereby improve metacognitive language learning strategy use and motivation. There were two sections to the study, quasi-experimental and longitudinal. The quasi-experimental study was carried out with the 55 students in the experimental group and 22 students in the control group. The anticipated effects of the Portfolio Programme on the students' use of metacognitive language learning strategies and on the feeling of control over the learning process could not be confirmed. Yet, in surveys and interviews, the students from the experimental group reported some improvement with regard to these variables. In addition to the expected effects of the Programme, the students' own accounts of the experiences were investigated. It was found that the reported effects sometimes differed from those derived from the theory. In-depth interviews with individual students suggested that only students with a specific set of learner characteristics can benefit from the Programme. For the longitudinal study, the learners were asked at different points throughout their Degree Course about the effects of the treatment they experienced in their first year at University. Thus, both immediate and long-term effects were recorded and all data was triangulated. Since the Portfolio Programme builds on experiential learning and awareness of the learning process, some effects took time to manifest themselves in the learning experience. The reported long-term effects therefore differed from those reported immediately after the treatment. Finally, the relationships between the individual effects were investigated with the aim of subjecting the underlying theory to critical analysis. Although there was a productive synergy of the individual effects of the Portfolio Programme, further research is necessary to pinpoint the areas most efficiently targeted for learner development.