It was discovered in 1858 and later excavated by a team led by the geologist William Pengelly, who found proof that humans co-existed with extinct British fauna.

[3] Windmill Hill Cavern was a chance discovery in 1858 by builder John Lane Philp, who was searching for a pickaxe that had fallen into a hole in the ground during construction of a house on Mount Pleasant Road in the northwestern part of Windmill Hill and incidentally came across the cave.

[2][4][5] Upon hearing about Philp's discovery, the Geological Society of London drew up a lease to secure an excavation of the cavern.

After studying the flint artifacts at the Somme River Valley's gravel terraces, the more sceptical members of Pengelly's team, such as Joseph Prestwich, found the proof that they sought that humans and extinct British animals had once lived amongst each other.

[4] Remains of animals found in the cave included those of extinct species such as aurochs and woolly mammoth, as well as still extant taxa now absent from Europe, such as the spotted hyena.