POPE Benedict XVI will step down today after nearly eight years as leader of the world's 1.2bn Roman Catholics.
The Pope is due to meet cardinals before being formally bid farewell later by Cardinal Tarcisio Bertone and other members of the Vatican's Secretariat of State in Rome.
He is then due to fly by helicopter to Castel Gandolfo, the Pope's summer retreat, with the empty office of Pope, or the Sede Vacante, formally declared at 7pm.
The 85-year-old Pontiff, who was elected in 2005 following the death of John Paul II, shocked the world earlier this month by announcing he was to resign on grounds of age and increasing frailty.
He is the first Pope to resign in nearly 600 years.
The outgoing Pope held his last general audience in St Peter's Square yesterday in front of a huge crowd.
He recalled moments of "joy and light" but also times of difficulty when "it seemed like the Lord was sleeping".
Benedict XVI will be known as 'Pontiff emeritus' or 'Pope emeritus', after he has resigned and will keep the title of 'His Holiness, Benedict XVI'.
He will dress in a white cassock without the mozzetta, or elbow-length cape, and will no longer wear the red papal shoes.
His 'Fisherman's Ring', the special signet ring that contains the Pope's name and is impressed to validate certain official documents, will be destroyed, along with the lead seal of the pontificate.
The Pope is due to return to Rome in April to live in a convent in the Vatican.
Earlier this week, the Pope changed the rules of the conclave that will elect his successor, allowing cardinals to bring forward the start date if all of them arrive in Rome before the usual 15-day transition between pontificates.
An estimated 115 cardinals are expected to take part in the conclave, which takes place in conditions of secrecy in the Sistine Chapel.
It was revealed that he is 'grateful' for the prayers of British Catholics following the announcement that he was to retire.
A message from the Vatican to the Archbishop of Westminster, Vincent Nichols, said the Pope continued to give thanks for the 'many graces' he received during his four-day visit to Scotland and England in 2010.
"He recalls with gratitude the welcome extended to him on his historic visit to your country, and he continues to give thanks to God for the many graces received during those four days," the letter said.
British Catholics have no vote following the resignation of Cardinal Keith O'Brien as Archbishop of St Andrews and Edinburgh on Monday amid allegations – which he denies – of inappropriate behaviour towards fellow priests.
Cardinal Cormac Murphy-O'Connor, the former leader of Catholics in England and Wales, will take part in pre-conclave meetings, which are expected to start on Monday. At 80, he is ineligible to cast a vote.
The meetings are expected to tackle issues such as the need for reform and renewal in the Church following a series of scandals, including the leaking of documents last year from the Pope's study showing infighting within the Vatican bureaucracy.
The Catholic Church worldwide has also been rocked by clerical child sex abuse scandals in recent years.
The date of the conclave's start is important because Holy Week begins on March 24, with Easter Sunday on March 31.
To have a new Pope in place for the Church's most solemn liturgical period, he would need to be installed by Sunday March 17, a tight deadline if a conclave were to start on March 15.