This is a weird one. As told to William of Malmesbury, with reference to a miracle performed by Dunstan, Archbishop of Canterbury:
Dunstan "was able to lighten the woes of his sons by great miracles. One of these I have not seen in writing, though I recently heard it narrated by a monk of Christ Church. A thief, condemned to fall to his death, called on the aid of St Dunstan; his eyes already blindfolded, he was pushed away by his executioners and leapt into the chasm, but without coming to any harm. The blessed Dunstan spoke with him in person there, and removed his bandages. The poor man, heartened by this help, found his way along rough paths to higher ground; an invisible hand on his back supported him as he clung to the cliff-face, and prevented him slipping backwards". (p.15, i.20)
This is "apparently the earliest reference to the customary local mode of execution called ‘infalisation’, according to which felons were thrown from a cliff called Sharpeness at Dover" (William of Malmesbury, Gesta Pontificum Anglorum, ed. and trans. Michael Winterbottom, vol.II, p.33).
Hardcore Kentish justice!