The “long wall” after which Long Wall Street is named is not as might be expected at first glance the very visible fifteenth-century wall of Magdalen College that today dominates the entire length of the street on the east side, but the hidden twelfth-century City Wall to the west (shown below from inside New College).
This wall became redundant as a fortification in the seventeenth century, and houses were built along the west side of Long Wall Street. This ancient wall still separates the back gardens of the houses on the west side of Long Wall Street from New College to the north and St Edmund Hall to the south.