Accession
Upon the death of a Sovereign, his or her heir apparent or heir presumptive immediately and automatically succeeds, without any need for confirmation or further ceremony. Nevertheless, it is customary for the accession of the Sovereign to be publicly proclaimed, first in London, and then in York and other cities. The anniversary of this is observed throughout the Sovereign's reign as Accession Day.
Formerly, the new Sovereign proclaimed his or her own succession. After Elizabeth I died, however, an Accession Council proclaimed the succession of James I, who was in Scotland at the time, to the throne of England (he was already King James VI of Scotland at the time). This precedent has been followed in each case since; now, the Accession Council normally meets in St. James's Palace. Proclamations since James I's have usually been made in the name of the Lords Spiritual and Temporal, the Privy Council, the Lord Mayor, Aldermen and citizens of the City of London and "other principal Gentlemen of quality", though there have been variations in some proclamations. Elizabeth II's proclamation was the first to also make mention of representatives of members of the Commonwealth.
After an appropriate period of mourning has passed, the Sovereign is also crowned. Coronations are held in Westminster Abbey. The Archbishop of Canterbury normally officiates, though the Sovereign may designate any other bishop of the Church of England. A coronation is not necessary for a Sovereign to reign; for example, Edward VIII was never crowned, yet was the undoubted king during his short reign.
Read more about this topic: Succession To The British Throne