It appears.. from the ancient and authentic records, that during the time St. Elwitus led the life of a hermit at Llanhamelach, the mare that used to carry his provisions to him was covered by a stag, and produced an animal of wonderful speed, resembling a horse before and a stag behind.
Was this a deliberate intervention by St Illtyd, who felt his groceries weren’t getting delivered fast enough? This is from the Itinerary of Archbishop Baldwin through Wales, by Giraldus Cambrensis, which was written after their journey in 1188.
It’s in chapter 2 and you can read it online at V Wales
vwales.co.uk/ebooks/itinerary.htm