Lepers were outcasts in the medieval world. They generally lived outside city walls and used a clapper or bell to warn others of their approach.
One of Jesus’ miracles had been cleansing a leper, and he had washed the feet of his disciples. Caring for lepers, and sometimes even washing their feet, became acts of Christian charity. According to the chronicler, Aelred of Rievaulz, Matilda of Scotland, wife of King Henry I, and queen of England from 1100-1118 washed the feet of lepers at her Easter Court in 1105.
To find out what part lepers play in The Viscountess and the Templars, I hope you will read the book when it is published.
In the meantime, please consider nominating the book on Kindle Scout.
People today still wash the feet of lepers as recounted in this blog post: