Pope Benedict XVI's Papacy Enters Final Hours

Pope Benedict XVI's tenure as leader of the world's Catholics is drawing to a close.

The 85-year-old stands down as Pontiff after nearly eight years and at a time when the Church is mired in controversy.

This morning, more than 100 cardinals said their farewells to the Pope at a gathering in the Clementine Hall in the Apostolic Palace.

In an unexpected speech, he promised "unconditional reverence and obedience" to his successor during the gathering and urged his cardinals to work in unity as they select the next pope.

Just before 4pm UK time, Benedict will leave his apartments for the last time, give his thanks to the senior staff who have been by his side during his papacy, and then make his way to the Vatican helipad.

From there he will fly to Castel Gandolfo - the Pope's retreat on the outskirts of Rome.

Then, at around 4.30pm, he will make his last brief appearance on a balcony in front of an expected crowd of around 7,000 before withdrawing from public life for good.

At 7pm the doors of the villa will close and the Swiss Guard will stand aside marking the end of Benedict's papacy.

From then on he will be known as Emeritus Pope and devote his days to prayer and meditation.

Once renovations are complete, Benedict will move to a monastery in the grounds of the Vatican.

He will still wear a white cassock normally reserved only for pontiffs, but without a doubled shoulder cape.

Spokesman Frederico Lombardi said he has chosen to swap his trademark red shoes for a brown pair given to him by artisans in Mexico during a trip last year.

Edward Pentin, from the Catholic Herald, said Benedict will live a monk's life and not interfere in the work of his successor.

The next pope will be chosen by secret ballot during the conclave of eligible cardinals who will vote in the Sistine Chapel.

Pope Benedict XVI's departure from the Vatican sets in motion a timetable of centuries-old traditions in what is an unprecedented resignation in modern Catholic history.

After 7pm on Thursday, the Catholic Church enters a period known as "Sede Vacante" (vacant See) during which a senior cardinal takes over interim powers until a new pope is elected.

That cardinal, referred to as the camerlengo or chamberlain, will be Italy's Tarcisio Bertone.

The camerlengo has traditionally had the role of officially certifying the death of a pope - once carried out by tapping the pontiff's forehead three times with a special silver hammer and calling out his birth name.

He is also charged with destroying the Fisherman's Ring - a gold signet ring specially cast for each new pope - which symbolises the end of a papacy.

From Monday, cardinals from around the world will hold a series of meetings known as general congregations.

The meetings are aimed at identifying priorities for the Roman Catholic Church for the future, but are also a good way of vetting possible candidates for next pope.

The cardinals then meet in a secret conclave to choose the next pope under a system adapted in the 13th century.

All conclaves have been held in the Sistine Chapel and the cardinals are sworn to absolute secrecy under pain of ex-communication during voting.

Two ballots are held in the morning, and two in the afternoon, until one candidate wins two-thirds of the votes.

At the end of each session, the ballots are burned in a stove by the chapel, releasing smoke above the Apostolic Palace. The smoke is black after each unsuccessful ballot, white once the vote succeeds.