Queen Elizabeth will pay tribute to inspirational unsung heroes in her Christmas Day broadcast to the Commonwealth on Sunday.

The 90-year-old monarch will put the focus on "ordinary people doing extraordinary things", according to the text of her annual message.

The head of the Commonwealth will urge people to achieve "small things with great love" in the speech, which is an integral part of Christmas Day traditions in Britain, and for millions around the world.

"I often draw strength from meeting ordinary people doing extraordinary things: volunteers, carers, community organisers and good neighbours; unsung heroes whose quiet dedication makes them special," she said, in the pre-recorded message.

"They are an inspiration to those who know them, and their lives frequently embody a truth expressed by Mother Teresa.

"She once said: 'Not all of us can do great things. But we can do small things with great love'."

Recalling the Rio 2016 Olympics, Queen Elizabeth was to pay tribute to Britain's 67 medallists who propelled the country to second in the medals table -- the kingdom's best performance in an away Games.

"There was a time when British Olympic medal winners became household names because there were so few of them," she said.

She said the athletes spoke of being inspired by previous generations, and were now inspiring the next.

The monarch also singled out Grenada, the Bahamas, Jamaica and New Zealand -- four countries where she is also queen -- which won more Olympic medals per head of population than other nations.

No mention of Brexit

Though she recalled the Games and her 90th birthday celebrations, the head of state did not mention the referendum in which Britain voted to leave the European Union, the dominating feature of 2016 in the UK.

She chose to focus on smaller-scale decisions instead.

"Even with the inspiration of others, it's understandable that we sometimes think the world's problems are so big that we can do little to help," she said.

"On our own, we cannot end wars or wipe out injustice, but the cumulative impact of thousands of small acts of goodness can be bigger than we imagine."

The royal family gather for Christmas at Queen Elizabeth's private Sandringham estate in Norfolk, eastern England.

As per tradition, the royal family were expected to walk to church together on Christmas Day.

Tradition began in 1932

Queen Elizabeth, who is the supreme governor of the Church of England, often refers directly to her guiding Christian faith in her Christmas message.

"Christ's example helps me see the value of doing small things with great love," she was to say in conclusion.

"The message of Christmas reminds us that inspiration is a gift to be given as well as received, and that love begins small but always grows.

"I wish you all a very happy Christmas."

The queen's Yuletide message is an annual tradition screened at 1500 GMT in Britain on Christmas Day, as many families recover from their turkey lunch. It is broadcast at convenient local times across the Commonwealth.

It is one of the rare occasions where she speaks from the heart, without having to consult government ministers.

The tradition was started on radio by her grandfather king George V in 1932. It is now filmed in advance in high-definition and posted on YouTube.

At Sandringham, Queen Elizabeth leaves the room when it comes on television, preferring to watch it alone.