The beginnings of The Order of St John lie back beyond the First Crusade to the Holy Land in 1095. When they captured Jerusalem, the Crusaders founded a hospice, the Hospital of St John of Jerusalem, run by a group of monks led by Blessed Gerard.

The Crusaders gave the hospital land and money and in 1113 the Pope recognised it as an independent religious order of monks and nuns, The Order of St John, whose special task was to care for the sick. In the next 800 years, a number of "branches" of the original Order of St John rose and faded throughout Europe. The Order in England, from which the Priory in New Zealand is descended, finally re-established itself in 1831 after centuries of persecution and decline.

It was incorporated by Royal Charter of Queen Victoria in 1888, with the Queen as Sovereign Head of the Order. This Royal Charter also established St John as a royal order of chivalry.

The St John Eye Hospital in Jerusalem, which performs about 5000 major eye operations each year and treats 50,000 outpatients, has a training school for postgraduate doctors and nurses and a research institute. It has an 'outreach' programme to train villagers in primary health care. The Priory in New Zealand gives financial support to the hospital and recruits doctors and nurses to serve there.

The St John Ambulance Association was founded in England in 1877 to provide ambulance transport and instruction on first aid to the public at home and at work. The first ambulance textbook was published in 1878 and soon afterwards ambulance equipment, such as first aid hampers and wheeled litters, was available from the Chancery at St John's Gate in London.

The St John Ambulance Brigade formed in England in 1887 as an organisation of trained volunteers, providing a service in first aid and ambulance transport at public events. Groups of "first aiders" holding the Association's certificate began to group together as "corps" - now known as divisions.

The International Headquarters of The Order of St John are at St John's Gate, Clerkenwell, and London. There are Priories in Scotland, Wales, South Africa, Canada, Australia, New Zealand, England and the United States of America and Commanderies in Northern Ireland and Western Australia.

Foundations of the Order operate in 40 other countries, mostly members of the Commonwealth.