This paper highlights a hitherto unreported change in progress among northern speakers of British English, with increasing post-nasal [ɡ]-presence in words like sing or wrong pre-pausally. The factors that condition this innovation are unclear due to collinearity between various boundary phenomena. The right edge of phrasal prosodic categories may be associated with boundary tones, final lengthening, and pause; consequently, the variable presence of [ɡ] appears to be affected by prosodic boundary strength, segmental duration, and the presence and duration of a following pause. These factors are teased apart through analysis of an elicitation task from 30 northern speakers, which reveals that [ŋɡ] clusters are conditioned most strongly by pause. Post-nasal [ɡ]-presence is only licensed when the following consonant-initial word is temporally distant, showing only minimal sensitivity to prosodic boundaries directly. The surface effect of segmental duration arises only indirectly through its collinearity with pause duration. Current theoretical approaches to external sandhi emphasize a range of different factors, including phonological representations of prosodic constituency, phonetic parameters like segmental duration, and psycholinguistic mechanisms of production planning. This paper provides quantitative evidence from an under-reported feature of northern English that bears directly on these debates.