equality." The United Kingdom was formed by the union of previously independent countries in 1707, and consequently most of the largest religious groups do not have UK-wide organisational structures. While some groups have separate structures for the individual countries of the United Kingdom, others have a single structure covering England and Wales or Great Britain. Similarly, due to the relatively recent creation of Northern Ireland in 1921, most major religious groups in Northern Ireland are organised on an all-Ireland basis. History Pre-Roman forms of religion in Britain included various forms of ancestor worship and paganism. Little is known about the details of such religions (see British paganism). Forms of Christianity have influenced religious life in what is now the United Kingdom for over 1,400 years. It was introduced by the Romans to what is now England, Wales, and Southern Scotland. The doctrine of Pelagianism, declared heretical in the Council of Carthage (418), originated with a British-born ascetic, Pelagius. During the Anglo-Saxon settlement of Britain in the 5th and 6th centuries, paganism was re-established; Christianity was again brought to Great Britain by Catholic Church and Irish-Scottish missionaries in the course of the 7th century (see Anglo-Saxon Christianity). In 601 AD, Pope Gregory I ordered images of pagan gods in England to be destroyed, but not the temples, which should instead be used as places of worship of the Christian God. England was nominally Christianised by the end of the 7th century, during which paganism was banned by the Church. Despite this, pagan practices such as leaving votive offerings at standing stones, trees and wells, persisted at least into the 11th century, prompting new penitential laws across England that aimed to suppress the surviving folk beliefs. Insular Christianity as it stood between the 6th and 8th centuries retained some idiosyncrasies in terms of liturgy and calendar, but it had been nominally united with Roman Christianity since at least the Synod of Whitby of 664. Still in the Anglo-Saxon period, the archbishops of Canterbury established a tradition of receiving their pallium from Rome to symbolize the authority of the Pope. Paganism was re-introduced to regions of the British Isles in the 9th century by Scandinavian settlers who established the Kingdom of the Isles and the Danelaw. The timeline for the conversion of the settlers varies, with the Danish leader Guthrum baptised in 878 AD in accordance with the Treaty of Wedmore. Orkney, on