Queen Elizabeth's annual Christmas address invokes the anniversaries of the D-Day invasion and the moon landing, as well as the birth of her eighth great-grandchild, to deliver a message of peace and reconciliation.

The 93-year-old monarch quoted astronaut Neil Armstrong's famous words of having made "one small step for man, one giant leap for mankind" when he stepped onto the moon during the Apollo 11 mission some 50 years ago.

"It's a reminder for us all that giant leaps often start with small steps," the Queen said.

She did not make any direct references to modern-day political issues, including the recent U.K. election that saw Prime Minister Boris Johnson's Conservative Party secure a resounding victory, paving the way for Brexit. But she noted events this spring that marked the 75th anniversary of D-Day, which saw former foes set aside their differences and come together for "friendly commemorations.

"Such reconciliation seldom happens overnight. It takes patience and time to rebuild trust, and progress often comes through small steps," she said.

The Queen attended Christmas Day church service at the Church of St Mary Magdalene on Sandringham estate on Wednesday. (Stephen Pond/Getty Images)

"By willing to put past differences behind us and move forward together, we honour the freedom and democracy once won for us at so great a cost."

Wearing a blue dress and surrounded by portraits of her family, the Queen noted the birth this year of Archie, Prince Harry's first child, with Meghan, the Duchess of Sussex, and her eighth great-grandchild. Turning to Christmas, she said the story is, at its heart, about the birth of a child, an event that goes "overlooked' in Bethlehem.

"But in time, through His teaching and by His example, Jesus Christ would show the world how small steps taken in faith and in hope can overcome long-held differences and deep-seated divisions to bring harmony and understanding," she said.

"Many of us already try to follow in His footsteps. The path, of course, is not always smooth and may at times this year have felt quite bumpy. But small steps can make a world of difference."

WATCH | In Christmas message, Queen Elizabeth encourages 'small steps' to create change:

Queen Elizabeth invokes D-Day, Apollo 11 mission in annual Christmas address urging her subjects to set aside their differences. 7:41

The carol It Came Upon a Midnight Clear speaks of Christ coming into a "divided world," she went on, but also carries the angels' timeless message of "peace and goodwill.

"It's a timely reminder of what positive things can be achieved when people set aside past differences and come together in the spirit of friendship and reconciliation," she said.

"And as we all look forward to the start of a new decade, it's worth remembering that it is often the small steps, not the giant leaps, that bring about the most lasting change."

Prince Andrew keeps low profile

As is customary, the Queen spent Christmas morning at Sandringham Estate in Norfolk, eastern England, joined by other members of the Royal Family. That group did not include Harry and Meghan, who are spending the holidays with their son in Canada.

Prince Andrew also avoided the limelight on Christmas Day by skipping the Royal Family's traditional mid-morning walk to church and attending an earlier service with other relatives.

Andrew, the middle of the Queen's three sons, has kept a low profile since he stepped down from royal duties last month in the wake of a scandal over his friendship with convicted sex offender Jeffrey Epstein.

He was filmed walking along a path with his brother, Prince Charles, first in line to the throne, to St Mary Magdalene church near the Sandringham Estate, in time for the 9 a.m. local time service.

Andrew did not join other members of the family when they walked to the 11 a.m. service, one of the staples of the royal calendar.

Prince George, Princess Charlotte, and Prince William and Kate, the Duke and Duchess of Cambridge, leave after the Royal Family's traditional Christmas Day church service on Wednesday. (Ben Stansall/AFP/Getty Images)

Media reported Andrew had made a personal decision to miss the main service and stayed in the house with his father, Prince Philip, who had been released from hospital just days earlier. Buckingham Palace declined to comment.

The royals who were at the service were greeted by several hundred well-wishers outside the church grounds. After the service, William, Kate and their two children mingled with the crowd to exchange Christmas greetings.

Gemma Clark, who was in a wheelchair, gave Charlotte an inflatable pink flamingo and received a hug in return. She said the flamingo was called Felicity, but that Charlotte was free to give it another name.

"It made my day," Clark added. "I've never seen the Royal Family, ever."

After church, the royals gathered in Sandringham House for a gala turkey lunch.

Prince Philip, the Duke of Edinburgh, who released from hospital on Tuesday after going in the previous week, had been receiving treatment for what Buckingham Palace called a "precautionary measure" to treat a pre-existing condition.

Prince Philip leaves the King Edward VII's Hospital in London on Tuesday. (Hannah McKay/Reuters)

He walked out of King Edward VII Hospital and shook hands with a nurse before getting in the front passenger seat of a Range Rover car and being driven away.

Philip retired from public life in August 2017, but has appeared at a handful of official engagements since then.

Also on Wednesday, Kensington Palace released a new photograph of Prince William and his daughter, Princess Charlotte, as well as her siblings Prince Louis and Prince George.

The photograph was taken earlier this year by Kate, the Duchess of Cambridge, while the family was in Norfolk.