Devensian limit in West Wales

This represents my current thinking on the Devensian limit in West Wales, dated at around 20,000 yrs BP.  The yellow line shows the limit of the Irish Sea Ice Sheet.  The purple line shows the extent of Welsh ice at about the same time.  The orange arrows show the assumed directions of ice movement during earlier glacial episodes, for example in the Anglian and Wolstonian Glaciations. (The Anglian is assumed to have been a time of very extensive ice cover.  There is more doubt about the Wolstonian.)

Note that in the "unglaciated" part of Pembrokeshire in the Devensian, there may well have been a small ice cap on Preseli at the peak of the glacial episode, and also very extensive perennial snowfields elsewhere.  If you had flown across the landscape at the time in the Tardis, you might not have seen any clearly defined ice edges.