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During the Last Glacial Maximum, the British–Irish Ice Sheet was dominated by a number of accumulation centres, including a terrestrially based, semi-independent icecap centred on Wales. The dynamics of this Welsh Ice Cap (WIC) over the last glacial period are still relatively poorly understood, with few studies taking into consideration the dynamic evolution of the icecap as a whole. Here we contrast results from two modelled reconstructions of the WIC in conjunction with the wider glacial geomorphological record to elucidate understanding of its form, extent and dynamics. Model output was analysed to yield zones of high basal motion and the spatial distribution of potential glacial erosion. We conclude that coherent flowsets of streamlined bedforms are linked to fast-flowing outlets dominated by basal sliding. Large-scale changes in dynamics are discussed, with a number of possible major advances proposed over the glacial cycle. Maximum ice thicknesses of ∼1200 m in Mid Wales indicate that all mountain summits were probably ice-covered during the Last Glacial Maximum, even if it was with a thin protective mantle of cold-based ice, leading to landscape preservation of these upland zones. The distribution, dynamism and landscape modification related to the WIC are further discussed at the regional scale. Model predictions of glacier distribution through the Younger Dryas stadial accord well with geologically reconstructed limits at this time.