[1] It was established in 1191, at Acre, after the capture of that city by Richard I of England and Philip II of France.

After the capture of the city, William, Chaplain to the Dean of St. Pauls Cathedral at London, formed a small religious order, its members taking vows of poverty, chastity and obedience.

The purpose of the Order was tending to the sick and wounded, and burying the Christian knights who fell in battle in the Holy Land.

To that, William, as Prior of the Order, added the purpose of raising funds to ransom captives from the Muslim armies of Saladin.

The success of the Order enabled it to establish a church and hospital which was dedicated to St Thomas Becket, Archbishop of Canterbury.

[3] According to Pope Gregory IX this was done thanks to the indulgence of the existing canons of the Hospital of St Thomas in Acre.

During this period, about the year 1279, as the purposes of the Knights of St Thomas shifted from that of religious hospitallers to a more military role, the position of Prior, the Order's religious head, lost its pre-eminent position to the Masters of the Order who acquired property and privileges, and created a provincial organisation in the British Isles, with its headquarters in Cheapside London and a subordinate preceptory in Kilkenny.

By 1279 it appealed to Edward I for funds, and their financial problems seem to have prompted the proposal to merge with the Knights Templar.