The Governor, the Honourable Frances Adamson AC, and Premier Peter Malinauskas joined other dignitaries and more than 450 members of the public in the Cathedral with several hundred watching the livestream outside.
Archbishop O’Regan and other faith leaders were invited to read prayers at the service.
In his address, the Anglican Archbishop of Adelaide, Geoff Smith, said even though she was based in England, she was “our Queen and she served faithfully for more than 70 years”.
“She visited South Australia seven times and worshipped in this Cathedral on four occasions.
“There were many crises at home and abroad during her 70-year reign, and many personal challenges, yet through it all she carried out her duty faithfully and well, without ego, serving right to the end of her long life.”
Archbishop Smith recalled the Queen’s first Christmas address in December 1952, when she asked ‘whatever your religion may be, to pray for me on that day (her coronation) – to pray that God may give me wisdom and strength to carry out the solemn promises I shall be making, and that I may faithfully serve Him and you, all the days of my life’.
“Today we gather both inside and outside the Cathedral to thank God for answering those prayers, and to give thanks to God for the life and service of the Queen,” Archbishop Smith said.
In his homily on the national day of mourning, Archbishop O’Regan said despite the Queen’s age the suddenness of the news of her death has “left us all a little bit ill-footed”.
He said all the tributes and reflections that had flowed for the Queen had reflected a deep sense of gratitude for a life of tireless service and “a life well-lived”.
President of the Australian Catholic Bishops Conference, Timothy Costelloe SDB, said Queen Elizabeth was never reticent about acknowledging her Christian faith.
“Her annual Christmas message invariably focused on Jesus Christ as a model of humble and generous service,” he said.
“It was a model she strived to emulate throughout her long life.”Jump to next article