This book explores the evolution of modal constructions of necessity and obligation in New Englishes. Focusing on Singapore English, analysis of corpus data reveals lower levels of grammaticalization compared to its lexifier, British English. This trend is explained through the lenses of a “pan-stratist” model, which considers a spectrum of forces influencing the dynamics of contact. On the one hand, cognitive mechanisms seem to favour the selection of less grammaticalized (and more transparent) variants from the lexifier. On the other hand, the substrate is positioned as a background force, actively contributing to the selection of new material to address functional gaps in the system.