After dividing from Alexander and the others in search for Perceforest, the English knight Claudius and the Scottish lord Estonné rode for three days without incident - or indeed food. They were hungry - unsurprisingly, though the people in those days were of a stronger constitution and were not so richly fed.
Alexander the Great gets extremely lost going to India and ends up landing in Britain instead, and his knights he leaves behind form an original picture of chivalry on the island far before Arthur - that’s the premise of the 14th century Old French Perceforest.
This incursion of a historical figure from the eastern Mediterranean is unrelated to that whole Trojan history bit - which also happens in this tale’s timeline. This doesn’t seem to have been copied by a lot of later takes, but it’s got entertaining bits and certainly gives some options for ancient ruins and the like.