The book offers a significant theoretical and empirical contribution to the ongoing vigorous debate on loanword phonology, its major mechanisms and various interpretations. It provides an in-depth analysis of a rich body of novel experimental data on online adaptation of Polish consonant clusters, absent in English, by native speakers of British English. The analysis is couched within the framework of Optimality Theory. The author argues for the phonological approach to loanword adaptation as well as for the core-periphery structure of the English lexicon and shows that the proposed perspective allows for a deep insight into the nature of the collected language data.