Cardinal O'Brien speaks about his journey before leaving Scotland

Cardinal Keith O'Brien departed for Italy on Tuesday while Roman Catholics all over Scotland continued to mourn the passing of the pontiff.

Cardinal O'Brien is staying at the Scots College until the Pope's funeral in the Vatican at 0800 GMT on Friday.

Dr Alison Elliot, Moderator of the General Assembly in Scotland, will also travel to Rome to attend the funeral.

As a "Prince of the Church", Cardinal O'Brien will join the Papal Conclave to choose a new pope.

The Archbishop of St Andrews and Edinburgh will be only the second resident Scottish cardinal to participate in such an election since the Reformation.

Cardinal O'Brien has led Scottish tributes to the Pope since the pontiff's death on Saturday. On Monday he celebrated a Mass at St Mary's Cathedral in Edinburgh, attended by leading figures from Scotland's religious, political and civic life.

Speaking as he prepared to leave for Rome he talked of his mixed emotions about the journey.

WHAT HAPPENS NEXT Pope will lie in state until his burial on Friday Funeral on Friday at 1000 (0800 GMT) Election of new Pope begins 15-20 days after death

"I feel sadness at the loss of a great man who served the church to his last breath, happiness that he has gone to his eternal reward and trepidation as I join with my brother cardinals in the momentous task of selecting a new pope," said the cardinal, who was appointed by the Pope in October 2003.

"Like me, almost all of the 117 cardinals who will vote in the forthcoming conclave were appointed by Pope John Paul II.

"We have not taken part in a conclave before. We enter this process in prayer and reflection, asking the Holy Spirit to guide our actions and urging the faithful around the world to remember us in their prayers.

"To be called to elect the successor to St Peter and to play a part in the Apostolic Succession is an awesome responsibility, I am humbled by the trust placed in me and immensely grateful for the wave of support which has washed over me in the last 48 hours.

"I carry with me the hopes and prayers of many of my fellow Scots and in return I give them my promise, that throughout my time in Rome, I will remember them and pray for the intentions of Scotland and all its people."

The funeral of Pope John Paul II will take place on Friday

Nearly 200 cardinals will be involved in the consultations to elect a new pope but only the 117 of them who are under the age of 80 are entitled to vote in the extremely secretive election process.

John Paul II decreed that the conclave to elect his successor should not begin until at least 15 days have passed since his death but it cannot be delayed beyond 20 days.

Each cardinal has to swear an oath of secrecy - on a Bible - to ensure they reveal nothing about the election and are shut off from the outside world once voting begins.

In the past, cardinals were allocated makeshift "cells" with uncomfortable beds and chamber pots.

However, for the first time, they will enjoy modern hotel-style accommodation within the Vatican.

Initially, a cardinal will require two-thirds of the votes to be elected pope but after about 30 ballots, there is an option for deciding the election by a simple majority.

Cardinal O'Brien will not return to Scotland until a new pope has been voted into power in the Vatican.

The Moderator of the General Assembly in Scotland, Dr Alison Elliot, will also travel to Rome to attend the Pope's funeral.

Dr Elliot is undertaking a pre-arranged visit to Poland and the Czech Republic, and is presently staying in the Pope's home city of Krakow.

She will break from her planned itinerary on Thursday in order to travel to Rome and will return to the Czech Republic to resume her visit after the funeral of the late pontiff.

KEY AREAS WITHIN THE VATICAN 1: Papal Apartments: Where John Paul II died, 2 April 2005 2: Clementine Hall: Cardinals and other officials view Pope's body 3: St Peter's Basilica: Pope to lie in state and be buried here 4: Sistine Chapel: Cardinals to gather here to pick successor 5: St Peter's Square: Funeral mass to be held here on Friday